X resets after upgrade

Hi: About two weeks ago, I did a security update through YOU. Unfortunately, I don't remember what was updated, but ever since, X resets itself every once in a while, at random intervals. I can be reading emails, surfing the web, or working with Kdevelop. I will reset and I will lose my unsaved data. I upgraded KDE to 3.5 last week, thinking it might be a problem with KDE 3.4, but the problem is still there. If I use Gnome, I can work all day long, and no problem, so I must asume it's a KDE problem. Can anybody provide a suggestion so I can start looking for a solution? Best regards. -- Alfredo Cole-Tuckler