Matlab does not start, only as root.

Hello I just installed Kubuntu 10.04 on a different machine and then trinity. Everything went smooth, also my matlab installation went fine. Then I installed kscreensaver-kde3 (I am now on a different machine and don't have all the details) kscreensaver-xsavers-extra-kde3 kscreensaver-xsavers-kde3 and the trouble started, finally I had to do a sudo dpkg -i --force-all /var/cache/apt/archives/kscrensaver-Idont-the details.deb But the installation proceeded, but after that, I could only run matlab as root, otherwise I got a segmentation fault. When I use KDE4 Everything is fine. I repeated the matlab installation and the problem remains. Any idea? (Otherwise I have to reinstall the whole beast I am afraid) Thanks Uwe