Do you have the same issues with Ubuntu? I would try Kubuntu 11.10 64 bit, that's what I run and it's been flawless on my laptop. My desktop does have issues with it however but that graphics card has issues after every new distribution comes out. 11.04 64 bit kubuntu is running flawlessly on my desktop however.
From what I understand mint is a spin off of ubuntu, but I believe it's possible the exact changes mint has made may be part of your specific problem. It's worth investigating and trying out.