I would suspect that this is a display driver issue. Live Mesh installs its own display driver for use by RD on the host (your virtual machine would be the remote PC host) and if you are getting a black screen on connection and not a login screen for the remote desktop, I suggest filing a bug report with logs:
How to Submit Bugs and Live Mesh Logs
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator