PowerBook Stuck at Blue Screen?

Hi there, I have a old Powerbook G4 15" thats having the common blue screen with cursor on startup error. Since then, Ive wipe OSX off and has been using Linux on this powerbook for some time and it works fine and i always though the blue screen issue is just a normal software issue. Recently, i decided to reformat it back to OSX 10.5, the installation went on smoothly and it completed without any issues. After rebooting, it stucks a the "blue screen with cursor" again. Heres what ive tried and some facts.

- Reseted PRAM

- Reseted PMU

- Reformatted the HDD

- Boot in Normal Mode and it stucks at blue screen v cursor

- Verbose Mode shows no signs of errors and it continues to blue screen n sits there.
- Boot in Safe Mode and it works

- Works perfectly fine with Linux

- HDD tested OK

- RAM tested OK

- Ran Disk Utility to check for permission errors.

- Tried removing Airport card.

- DVD drive removed (after installation)
- Was able to boot from 10.5 Installation DVD

- Can't do AHT (Apple Hardware Test) as i do not have the original DVDs
- Warranty is obviously over.

Does anyone has any suggestions for me? Thanks!!