Quite possibly, Linksys changed the internals between v1 and v2.

It's an annoying feature that manufacturers do - while Linksys is generally good about it (different hardware has different model numbers), others have been known to switch production midstream. In general, if it works with say, v1, it may not work with v2 - the manufacturer may have swapped the internals.

It's worse with wireless devices - sometimes two units with identical model and version numbers may have completely different internals, so that one unit works, but the other unit doesn't.

That's why TiVo has their own wireless adapter - they can't count on people to buy the right one because it changes so quickly. Quite likely, you'll have to find another adapter that'll work...