PowerBook G4 Titanium 800 MHz Lock-up

My PB G4 Ti 800 MHz will start OK, but after ten minutes of being using any application, it locks-up and I have to do a reset to get control o f the computer. Also I can only the lower slot for memory. If I install memory in the upper slot only, I get the tone as if no memory is in stalled.

If I do not run any application the will not lock at all, but as soon as start an supplication the PB locks-u again :-(

My HD is not dying it works just fine. The problem I believe is with something on the motherboard. The computer will boot but I can only use it for about 10 minutes. Then it locks-up. If I shut it down by pushing the power button until it powers off and restart the computer it comes on again for another 10 minutes.

As for cleaning the upper memory slot, I have already this as well as clean the edge of the memory module.

Thought there was a recall a very long time ago PB G4 Ti computers that had problem with their memory slots.

Does anyone remember this type of problem?

Walter