I filed a bug a few weeks ago about a problem with Vista SP1.  The beta code caused a "black screen with mouse cursor" when the display driver came out of standby or hibernation.  The fix made it into the codebase yesterday, apparently, so the RC1 release has this problem.

Any time you resume from hibernation or standby with a multi-display configuration, or connect via TS/RDP (which causes a display driver resolution change) this appears to happen.  Starting/closing Media Center fullscreen is also a trigger for this problem.

Time to wait for the next build to show up on Connect...