Oh I know this error message, I see it quite often actually.
For me it usualy happens when I copy some files around (meaning: some file operation is in progress) and I drag some mp3 files to the winamp or it's playlist. But also not all the time (especially after it appeared once). The drag&drop reaches winamp though.
Anothe peculiar thing while we're at it.
Let's say I'm copying a folder named "Something big", and drag&drop "Someband - Somealbum" (a folder) onto winamp, I often see a message like:
This folder already contains a folder named "Something big". [the usual error message you get for moving a folder to some place where a folder with the same name already exists]
But I didn't touch the "Something big" folders, I only dragged the mp3 folder onto winamp (which starts to play instantly, btw...)
I don't know what happens if I say yes, yes to all or no, I mostly hit cancel. I don't
think that anything happens, but I don't know for sure. This message also only appears once.
Hope this helps for tracking the thing
bye
Creat