MSI stop working for me with driver 195.36.24 (195.36.31+ are too buggy for me) when I switch from kernel 126.96.36.199 to 188.8.131.52 or 2.6.36.
So there was a change in the kernel that make MSI not working anymore with nvidia driver.
MSI still working fine with other hardware.
AaronP : On my computer it's the contrary, it really works better with MSI enabled. With traditional interrupts I got after a few days :
kernel: [144397.974550] Disabling IRQ #16
and graphics start to be very slow until I unload and reload nvidia kernel module.