Boats travelling up and down Anduin and Lorien's isolation.
 

In the Fellowship of the Ring Aragorn stated that light boats used to travel from Wilderland down to Osgiliath. Surely if they had, they would have sailed past Lorien and contact would have been made with the elves that lived there?

Yet the impression is given that there was little or no such contact throughout the Third Age.

Men, like those of Rohan, treated Lothlorien superstitiously or even with fear. One might be aware that the Elves inhabited Lorien, but it's another thing altogether to visit such a perilous realm.

(Council of Elrond)

It's not that contact wasn't possible, it's entirely down to the estrangement of Men and Elves. In the late Third Age the only real contact between Men and Elves (outside of isolated and special cases such as the Rangers) appears to have been that between Thranduil's realm and Lake-town.

So no, you haven't discovered a plot hole.

Actually, Men other than those of Dale seem to have had some measure of contact with Lórien Elves.

For one thing, Haldir noted that he knew the Common Speech because 'there are some of us still who go abroad for news and the watching of our enemies, and they speak the languages of other lands'. I further posit that Lórien had occasional encounters with Men from Gondor, based on Faramir's words to Frodo.

The Two Towers The Window On the West

I wouldn't think the intercourse was a common thing, but both Lórien and Gondor seem to have derived some benefit from it, else it would have stopped altogether.

I would second what Inzil said. Probably there would be occassions, rather limited to individuals, where the two kin would meet. I am imagining it kind of in the same way it was happening with the Hobbits and Elves, for instance (and after all, Hobbits are also Men, only Small). The local Bilbos and Frodos of Gondor meeting local Gildors who go to pilgrimages to the Elven harbours of old by the Bay of Belfalas (the traffic would be much bigger, of course, while they were still in use), and who knows, maybe even one weirdo local Farmer Maggot from Eastfold could make acquaintances with some Lórien patrols. But such cases would be rare, not a rule.

Is it possible that the Woodmen and their kin who lived along the Anduin had some contact with the Elves of Lórien and/or Mirkwood?

And evidently the surviving Dúnedain of the North still had a very close relationship with the Elves (although that's the Elves of Rivendell, not of Lórien).

It seems it was in the south that there was the greatest estrangement, in Rohan and Gondor, which probably makes sense given the geographical separation.

Greatest estrangement
 

I agree with you here, Zigûr. It may have also been because both states were the main opponents of Sauron. The rulers of both, and in particular Gondor, would have been interested in people offering practical help, rather than those who kept mostly to themselves.

While there may have been those in Gondor who acknowledged the influence of Elvish culture on them, and respected what Elves had done in the past, they might (like Denethor II) have regarded them as fallen far from their past glories, and being irrelevant players in the present geopolitical situation.

One could perhaps blame Elrond and Galadriel somewhat, for not offering the rulers of Gondor and Rohan regular advice and intelligence reports.

Quite. The feelings of Men in the Third Age when they passed near Lórien are illustrated quite nicely by a passage from Cirion and Eorl..., (ii) The Ride of Eorl in UT:
(emphasis mine)

As we see here they had some folklore about Lórien and were probably aware that it was Elvish land, but their yearning to catch a glimpse of its beauty was mingled with fear, and their first reaction to the spreading mist was dismay at being touched by Elven magic. Even when the mist proved beneficial to them only his horse's instinct convinced Eorl that it was indeed harmless. (Borondir, on the other hand, seems to have known a little better, as is to be expected from an Gondorian.)

I suppose any Men of Rohan or the North travelling on the Anduin by boat would have felt much the same: they would marvel at the Golden Wood and whisper some old tales to each other, maybe tell their children and grandchildren about it with some pride, but landing on the western shore and making contact with the Elves was a wholly different matter and restricted to few individuals.

It might be a recursive situation: did communication fail between the Eldar and Gondor because of the estrangement, or was the estrangement caused by the lack of communication?

I think a substantial reason might be that for the majority of the Third Age the threats appeared to be deriving from different sources: Arnor and the Elves were troubled by Angmar and Dol Guldur, while Gondor fought the Haradrim and the Easterlings. Gondor's wars were also largely Sauron's doing, but less openly.

The relationship between North and South seems to have failed after 1975 when Gondor and the Elves destroyed Angmar. Despite their victory, the North-kingdom had ceased to exist, which may have severely limited any existing relationship between Gondor and the allies of Arnor in the north. Although the Nazgûl conquered Minas Ithil in 2002, Sauron retreated from Dol Guldur in 2063 (a side effect, and possibly an unfortunate one, of Gandalf's investigation there). The Watchful Peace ensued. It seems possible to me that, with Arnor gone and the West at (uneasy) peace, the Men of Gondor had no apparent reason to maintain contact with the Elves, and thus lines of communication failed. Even for the Dúnedain the ensuing four hundred years of peace would have seen several generations of Men come and go. By the time Sauron returned to Dol Guldur in 2460 and the Nazgûl began attacking Osgiliath in 2475 the relationship between Gondor and the Elves may have been virtually nonexistent because they had not needed one for about four centuries.
It's interesting to think that as Lórien was the first Elven realm heading north on that side of the Mountains, it may have been the main "contact" that many Men in the South and along the Anduin had with Elves or Elvishness, and its seemingly strange and unsettling qualities may have hindered an ongoing relationship, particularly as time passed and the lore of Men failed. Probably a reason the relationship between the Lake-Men (and, one assumes, the Men of Dale before them) and the Elves of Mirkwood was so much stronger and more comfortable than any between the Men of Rhovanion or Gondor and the Elves of Lórien was because there was no Ring in Mirkwood and therefore such "magic" was much less common and noteworthy.

Stronger trading relationship?
 

Perhaps, although I suggest that another factor was the stronger trading relationship that existed between the Lake-men and the Elves of Mirkwood. We read in The Hobbit of the Elves crewing the rafts down the Forest River to the Long Lake staying as guests in Lake-town. Also, there was a reference that relations were good between both peoples, other than squabbles over river tolls. This trading relationship, clearly advantageous for both, would have eroded the fears such Men had about such Elves. Perhaps the Men and Elves who worked on the water bonded over songs, perhaps after alcohol was consumed? :cool::D

A good suggestion
 

That's a good suggestion.:) I still think, however, that the Elves could have tried to keep communications open, to the extent of sending regular intelligence reports. After all, Elrond and Galadriel were supposed to be extremely wise and farsighted people; so it would have been in their interests to do this.:rolleyes:

Wonder why they never returned. The perils of the journey or the perils of Galadriel and Lothlórien to mortal men?

I would think the journey would have been the reason, with Lórien's relative nearness to Dol Guldur resulting in Sauron's minions being about the area.
Glóin said to Frodo in Rivendell that the journey from Dale would have been "impossible" if not for the Beornings, and those Gondorians would have been much nearer to the peril of southern Mirkwood.

It wouldn't seem that any Man of Gondor had actually entered Lórien, since Aragorn was presented as such a special case.