I think the important bit here Andru is the
ArchLinux
bit. I will be the first person to admit that there is a world of difference between OpenGl on windows and almost any linux 'distro' (call them that for simplicity and not anger mobs of users). Perhaps as linux is solely dependant on OpenGl for graphics? I dont know - but I believe it may not just be the card at fault.

A thought to keep in mind.