It seems quite a few people are experiencing the video glitch problem; Random flickering of maps and game pieces.
Try rolling back to an earlier Java revision. Java 6 Update 7 is known to work reliably I believe. Later updates included in Windows XP Service packs seem to cause issues.
I get the refreshing problem with the big new GB2/CB (awesome btw) module.
It only happens with the 25% setting so I can work round it.
My system monitor says I’ve got plenty of memory.
Strangely while the CPU does nothing while in 50% mode it is doing something really straining it in 25% mode
I’ll try the Java rollback