When I launch Steam or most games outside of steam the X server will crash and restart.
I am using the proprietary drivers for ATI as most games require them. I was able to play games like "Mark Of The Ninja" and "A Virus Named Tom" perfectly but Steam itself and other games like "Limbo" and Rocketbirds: Hardboiled Chicken" cause X to crash. I suspect I may be missing some 32 bit library's but I am not sure.
When I attempt to run Steam from Terminal X-Server crashes. hmaarrfk, are you also using an ATI card? If you are could you do a local search on your machine to see if you can recongize which i686 libraries you installed?