Nexys2 - any luck getting it running on a virtual machine?
I know it's a late reply but since I spent my whole day today trying to get this setup to work, I wanted to spare someone else the effort.
In short, the digilent tools communicate neither under OSX10.6.8, OSX10.9.4 nor under Win 8.1 -- with virtualbox that is (I used 4.3.14)

Turns out that this is a known limitation of virtualbox that persists since 2008.

FWIW, I have it now working using vmware player (using Win8.1) - it's is marginally slower than running on native Windows but it works quite well.