http://penischan.110mb.com/wakaba/thumb/ <-- They are being created as 0-byte files. This is wrong.
In other words, I haven't a clue. Something with the thumbnailer is fucked up. A first step to figuring out what's wrong might be to dig into the thumbnailing function in wakautils.pl
and putting in die
statements to see which thumbnailer it tries to use.