urgent MythTV crashes after installing Nvidia drivers

I've swapped repos from atrpms to Fusion and X and KDE starts ok but as soon as I start Mythfrontend X crashes back to Logon screen [ 1944.020] [ 1944.020] Backtrace: [ 1944.020] 0: /usr/bin/X (xorg_backtrace+0x4a) [0x80ac51a] [ 1944.020] 1: /usr/bin/X (0x8047000+0x6a598) [0x80b1598] [ 1944.020] 2: (vdso) (__kernel_rt_sigreturn+0x0) [0xb770640c] [ 1944.020] [ 1944.020] Segmentation fault at address (nil) [ 1944.020] Fatal server error: [ 1944.020] Caught signal 11 (Segmentation fault). Server aborting [ 1944.020] [ 1944.020] Please consult the Fedora Project support at http://wiki.x.org for help. [ 1944.020] Please also check the log file at "/var/log/Xorg.0.log" for additional information. any ideas on how to fix this or what to check? Paul