System was running fine for weeks on KDE 4.2. For some unknown reason after booting the system would log in and use KDE 4.X as desktop. The "bouncing" cursor would do it thing for a second or two then the system would lock up. Tried to close the session using the ctrl-alt-backspace method all to no avail. The mouse cursor would still move around the desktop, tough. Looked through all of the logs to see if I could find something showing what could me amiss but nothing was there that I could find. I ran a memory test and all is fine. So I then re-installed the system this time using only KDE 3.5 and the system worked like a champ. I then ran the install CD, did an update to install the KDE 4.1 packages, logged into system and the lock ups continue.

AMD Athlon 3000+
ATI Radeon VE
2g main memory

As an aside when I do have KDE 4.X installed and I boot into the failsafe system I don't experience the lockups. Any help would be appreciated.
Thanks in Advance