What you have experienced are kernel panics. These are unrecoverable errors encountered by the Mac OS. I wouldn't be so sure you don't have any hardware problems - in my experience, 80+% of kernel panics, especially repeated panics like you're getting, are caused by hardware.
Have you run the Apple Hardware Test function on your Mac?
Have you run a program such as MemTest to make sure your RAM is functioning correctly?
Have you tried running a general hardware diagnostic with a program such as TechTool Pro - one you can boot from CD/DVD?
Have you booted from the Mac OS X install disc, run Disk Utility, and checked your disk for file system errors?
These are all things I would try, not necessarily in the order I listed them.