From the Nox Message board at Westwood about the mouse 'sticking' problem (post by a Westwood employee):
This has been confirmed as a problem with Windows 2000 and DirectX. We have made Microsoft aware of the conflict and they have assured us that a fix is in the works. I would recommend checking www.microsoft.com/directx for any updated information. If we hear anything first, we'll post a message here.
I'm having the same problem.