Invisibility and the Ring!

[Maédhros]

This is why I think that Gandalf would be unafected by the "invisibility" of the Ring.
From the Letters of JRRT: # 246

Of the others only Gandalf might be expected to master him – being an emissary of the Powers and a creature of the same order, an immortal spirit taking a visible physical form. In the 'Mirror of Galadriel', 1381, it appears that Galadriel conceived of herself as capable of wielding the Ring and supplanting the Dark Lord. If so, so also were the other guardians of the Three, especially Elrond. But this is another matter.

I think that a maia would also be unafected by the "invisibility" of the Ring, but I think that you would need a maia of the same range of power of Sauron to master his ring.

[ January 27, 2003: Message edited by: Maédhros ]