FC2 and Firefox

Sorry for spaming the list with problems like this, but i have a strange problem with firefox and fc2. After installing fc2 (i had fc2test3 before with no probs at all) i have a problem launching e.g. firefox as normal user. i have no problems launching it as root but as user. I tried to install firefox via yum as well as from sources and always had the same problem - there is no errormessage or anything else. Even removing the .phoenix-dir from home-dir doesn't change anything. Can anyone help me with this? Thanks, Jörn