Alessia, the crash log that you attached doesn't seem related. It has two crashes, one from October, and another from November 4th, which I think was when it was still working. Also, the recent one indicates that aMule was indeed starting up properly, because it's a crash while you were attempting to view the comments on a downloading file.
So, I suspect that the crash on the 4th was actually the beginning of your troubles. It probably caused some aMule configuration file to become corrupted, and you were never able to restart after that.
To understand what's happening, it will probably be necessary to see what aMule prints out as it runs. One way to get this is to run aMule in the Terminal. To do that, control-click (AKA right-click) on the aMule application and select Show Package Contents. Navigate to Contents > MacOS and double-click on the "amule" icon. This will open a new window in Terminal and run aMule in there. All of aMule's text output, which is usually hidden, will be written to that window. Copy what is written there and paste it to a reply here.
If you prefer to just get aMule working again without trying to figure out the actual cause of the problem, here's what you should do. In the Finder, rename the folder ~/Library/Application Support/aMule to ~/Library/Application Support/aMule_old. Now, try launching aMule. Hopefully it will work just fine. Because you renamed its configuration directory, it will have lost all of its settings, and will have forgotten about any downloads you had in progress.
To recover the downloads you had in progress, first quit aMule. Then, copy the contents of your previous Temp folder (~/Library/Application Support/aMule_old/Temp) into the new Temp folder (~/Library/Application Support/aMule/Temp). To let you access any credits you had earned with other ED2K clients, you also copy the cryptkey.dat and preferences.dat files from your old aMule configuration folder to your new one. Now, launch aMule and it should know about your in-progress downloads.
I hope that helps.