log in a terminal as user, then  do a rm /root/.revdep* and then try again revdep-rebuild. after you do a revdep-rebuild be always sure that no .revdep files are present anymore in the /root/ directory. if there are some present then revdep will continue to cicle through them.
another option would be to run revdep-rebuild -i (which stands for --ignore) which would ignore the .revdep files in the /root/ directory. i personally prefer the first option since i know that there aren't any cached revdeped files. if it continues to cycle on the same rebuild after one rebuild then it might be the case of a bug like the one of the gcj use flag in gcc-4.1. try searching on the forum if that might be the case.