Ello there! Was googling the 2400 and found this post and thought id reply
My problems were similar but with Ubuntu. I cant remember which ones worked best between ATI's own drivers or the Open source ones, but with one of them anything with 3d graphics flickerd. From Google earth to secound life. Nexuiz to breakout. The flickering did always stop when i turned of desktop effects. I havent used Linux Mint yet (hoping to soon
) but if theres a way of turning of desktop effects like Compiz try that and see if things still flicker.