It appears the problem is that there's a part file that is completing (fully downloaded and being copied to its final destination) but the attempt to open the part file or create the destination file fails for some reason.
When aMule attempts to write a log message informing you of this, it tries to convert the filename from Unicode to ISO8859-1, but that conversion fails because the filename has characters which can't be represented in ISO8859-1. But aMule doesn't detect that conversion failure and attempts to use the result anyway, and crashes.
As a temporary workaround, if you know what part file is completing, you can move it to its destination manually and move its associated .part.met* files out of your Temp directory. If you don't know which it is, you might have to do a binary search. Move half of the files out of the Temp directory, try aMule. If it crashes, then the bad file is one of the ones you left in; if it doesn't crash, then the bad file is one of the ones you moved out. Keep cutting the candidate pool by half until you find the bad one. It's not pretty, but it works.

In the meantime, we'll fix the crash.