G3 with G4 upgrade card crashes a lot

[1madstork]

I have a blue and white G3 Power Mac that was originally 300MHz but my teacher put a 500MHz G4 upgrade card and upgraded the logic so it could see a 500MHz processor. Problem is, the mac has crashed a few times and told me I needed to restart the machine. Plus, when I tried to upgrade from 10.2 to 10.3 it locks up at different points in the upgrade and tells me to restart. And individual programs keep crashing on me not affecting the os. This happens in IE when I change web pages sometimes.
Is there a known issue with these G4 upgrade cards that causes flakiness? Could this be an issue in my logic settings?
Thanks for the help! This is my first post since I have newly acquired my first Mac (actually it's my wife's).

 

[immdb]

go here to check if your card has been reported (good or bad)

http://www.xlr8yourmac.com/G3-ZONE/cpu.html

Also, it could be bad ram causing the problem.

 

[1madstork]

go here to check if your card has been reported (good or bad)

http://www.xlr8yourmac.com/G3-ZONE/cpu.html

Also, it could be bad ram causing the problem.

The card's been reported good. I noticed somewhere else that OS X requires all the same frequency ram sticks. One of mine is 133MHz and the other three are 100MHz. I took the 133MHz stick out and tried the 100MHz sticks in different configurations and I'm still having the same problems. I'm still not sure what the solution is.