refreshing AGP Card Memory??

[Stone Gecko]

I have a GF4 MX440 Video card in 5.1_Release running KDE3.1.3 that keeps 
either locking up or putting vertical red/blue lines on the screen. 

Is there any way to manually refresh or repage the memory to see if that helps 
stop the problem? maybe a cron script?

any ideas? did the same with 4.8 Stable

thanks