I post the question here, since it looks like an installation problem to me.
when starting amule, after an unpredictable amount of time, the following line is thrown in the terminal window from which amule is started:
(amule:5214): GLib-CRITICAL **: Source ID 32366 was not found when attempting to remove it
the amule freezes, and the memory usage increases until the system crashes
how can that be fixed?