Hyper-V has been long known to not play well (pun intended) with 3D graphics cards, due to its type-1 hypervisor nature, which puts the virtualization layer between the Windows O.S. and the underlying hardware; when the role is enabled, the memory translation operations required to make virtualization work don't allow 3D drivers to perform as they should; in the article I linked above, Microsoft explicitly recommends to not use 3D graphics cards with Hyper-V servers, or, if that is actually needed, to not use their card-specific drivers and instead switch to standard VGA drivers, losing all 3D acceleration capabilities in the process.
A more thorough explanation of this issue, along with a viable solution, can be found here: recent CPUs with latest-generation hardware virtualization support are able to work around this issue using a technology called SLAT, allowing to make full use of 3D graphics card on Hyper-V servers without any performance issue, and even making possible things like RemoteFX. Here you can find a list of CPUs which support SLAT.
If your CPU doesn't support SLAT, then you should definitely not try to use any 3D graphics card together with Hyper-V: if the server doesn't crash, it will have terrible video performance anytime you try to use anything even vaguely 3D-related (like Aero desktop themes).
If, however, your CPU does support SLAT, then this is probably a compatibility and/or driver issue: your card is not present in the Hardware Compatibility List for Windows Server, so it is not guaranteed to work; however, as the O.S. kernel is the same as Windows 7 x64, it should work with proper and up-to-date drivers.
The fact that you are experiencing a system crash only after enabling the Hyper-V role makes me think you are running into the issue I was talking about at the beginning of this answer, i.e. your CPU not supporting SLAT.