None that can hurt him?

[Fingolfin II]

This question has plagued me for some time, so I'll now put it to you and see if you have any ideas or comments about it.

In The Two Towers, just after Aragorn, Legolas and Gimli meet Gandalf the White in Fangorn Forest, Gandalf says-

'Get up; my good Gimli! No blame to you, and no harm done to me. Indeed my friends, none of you have any weapon that could hurt me. Be merry! We meet again. At the turn of the tide. The great storm is coming, but the tide has turned.' (emphasis mine)

That sentence which I highlighted in bold has been my dilemma. Legolas' bow and Gimli's axe may not be able to hurt Gandalf, but surely Anduril can? If Narsil could pierce Sauron so sufficiently as to destroy his body while he was wearing the Ring, surely Aragorn's sword could hurt Gandalf, a Maia of lesser power?

Perhaps Tolkien made an error here, or Gandalf forgot about Anduril or meant that if Aragorn swung at him with Anduril, he could block it with Glamdring or his staff. Or maybe he means that Narsil has lost it's potency over the years or that Gandalf cannot be defeated in his new form as Gandalf the White by any power in Middle-Earth. If the latter of my suppositions is true, then I assume it would also be true for Sauron at the height of his power during the Last Alliance when he wielded the One Ring. It is said that 'none could withstand Aeglos and Narsil', but if that's true, it also stands to reason that if Sauron took hurt from Narsil, so too would Gandalf. Any ideas?