I recently added "Kiss - Music from 'The Elder'" to my music file... and Winamp v5.01 absolutely would not see it. That is to say, the audio library could see the "KISS" group... and would see the "Elder" album, and it could see there were 11 tracks in it... but it couldn't see the tracks themselves.
Deleted/re-added the folder, rescanned the index, no dice.
Upgrading Winamp to version 5.08 fixed the issue.
I mean, "The Elder" IS the most hated KISS album, but come on.