This is a problem that has plagued me for a while now, and only two things seem to fix it.
The issue is that when using a Windows 7 RDP client (mstsc) to connect into another Windows 7 system, you sometimes find you’re left with nothing but a black screen.
From this black screen you can’t do anything. The cursor seems to respond, but you can’t seem to bring up anything useful, nothing works.
So what’s the solution?
I found that if you hit CTRL + ALT + END inside the RDP connection this will bring up the same menu as when you hit CTRL + ALT + DELETE on a normal system.
When this menu appears, you can press cancel or “Start Task Manager”, which should bring it back to life.
If that doesn’t work, try disconnecting and reconnecting.
Failing that, I’ve found that sometimes, in “Options”, if you untick the “Persistent bitmap caching” under the “Experience” tab you’ll find yourself being able to connect without a blank screen.