I'm afraid I don't really know what's going on.
The next step in gathering diagnostic information is to get a CrashReporter log. Launch /Applications/Utilities/Console.app. In the toolbar, there's a button labeled "Logs" -- click it. That will reveal a tree-view of the available log files on your computer.
Navigate through that tree to ~/Library/Logs > CrashReporter > amule.crash.log. Press the Clear button on the toolbar. This clears the display, which will make it easier to see what is subsequently written to the log in the following step.
Now, try to launch aMule. It will probably crash just as it has been. When it does, a bunch of stuff should appear in the Console window that's showing amule.crash.log. Copy what appears and paste it to a reply.
Hopefully, that will help us figure out what's happening.