preset too large?

aha, worked after closing foobar and saving again..

To the best of my knowledge this happens when AVS leaks. It gets confused and thinks that the preset it is trying to load can't fit into memory because it has allocated too much already... I've had it before quite a few times, and I noticed that when developing APES it occurs at a much higher rate... usually because I write leaky code at first and then only spot the leaks later.

Could this be addressed by closing and restarting Winamp and/or AVS?

I don't know, maybe you could read this thread and find out. 😉