Well, moving the app support folder (~/Library/Application Support/aMule) out of the way should give you a fresh start, as you thought. So, if that isn't working, then something is very wrong. We need to start there.
You need to be more specific. For instance, crashing and freezing are two different things. Which is happening? When does it happen? Does it happen immediately when you start aMule, or only after certain events, or randomly after some time?
It will be useful to know what output aMule writes to the console.log when this happens. Also, if it crashes it would be good to see the crash report. If it freezes, collect a sample report by using Activity Monitor's Sample Process command.
