could not find any compatible direct3d devices

i am playing warrock from last 3 yr without any error . but 2 week ago i get this error dont no why .

i.e. Could not find any compatible Direct3d devices.

After this i also instal Direct3d 9 but this error still exit.

if i reinstall your game then it run 2 to 3 hours and then this error again pop up and game goes shut down . so it is requested to pls help me in this regard.