iBook crashes upon startup

[mlofoto]

I have an iBook G4 that crashes (black block that says I must restart) upon startup. Here's what I have done: I have run the hardware test, long version, and everything has passed. I have verified and repaired disk and permissions.
I have attempted to reinstall the OS (4) but after verifying the install disk, I get an error upon reinstalling. Went to another 10.4 install disk. It installed. Got the the welcome page, crashed with black screen again. I also attempted to hook up the laptop to my Macbook Pro through firewire, but it crashed by Macbook (only try that once!!!). Since it seems to pass all that tests, what could it be???
thanks

 

[Detrius]

Boot in verbose mode holding down command-v. Then, the actual panic information will be shown on the screen. Look for the kernel loadable modules in backtrace and list those off. That's what's likely causing your panics. If there's nothing, or if it's inconsistent, then you could have bad RAM.