#8 Can't use mouse and keyboard at the same time

[Pete Davis]

It appears that, in a class derived from NUnitFormTest,
attempting to use both the keyboard and the mouse
from within a test will cause a Win32 exception to be
thrown.

I've corrected the problem by wrapping the BlockInput()
calls and adding reference counting so it only calls
BlockInput(true) the first time and doesn't call BlockInput
(false) until the reference count has dropped to 0.

Maybe there's a better solution.