PowerBook G3 Lombard crashes using Mac OS X


I have a Lombard G3 PowerBook 400 mhz with 30 gig hard drive, partitioned with OS 9.2.2 on one side, OS X 10.2 on the other.
PC card for one firewire port.

Running in Mac OS X, it crashes when it gets a little too taxed by programs like Photoshop or is downloading software updates. That isn't good cause I have to do a total reinstall then.

I ran Memtest , a unix based ram tester and discovered the original 64 mb was bad and took it out. That left the machine less prone to crash on Photoshop start-up but that was about it.

The remaining 256 mb runs with flying colors using Memtest but the crashes continue. All I have to do is run Radial blur in Photoshop and it is toast.

I was told by an authorized Mac tech guy that some other component is bad on the laptop and needs to be replaced. He said it is a hit or miss to do this. He recommended getting rid of the machine and I don't want to have to buy another one right now. The Unix base in Mac OS X does not like any components that are not running perfectly.

Is there a way to test the other components? Any other options would be helpful. Thanks in advance!!