Fedora Core FC5
pgadmin3 1.4.2 (Mar 25 2006) installed by rpm. Same behavior with 1.4.1.
After reading some postings, installed gtk-qt-engine-0.60-8 via rpm, did not help
Bug is trivial to reproduce: click on help ? in toolbar or select Help|Bugreport
from menu. I'm sure there are other ways to crash as well.