I'm using a Dell Latitude E640, Windows 7 64-bit SP1 and a Dell docking station.
If I un-dock the laptop and later reconnect to the docking station, the mouse pointer can no longer be moved. I'm using a separate mouse and keyboard, both are corded USB models (mouse is a straightforward Dell model). They keyboard works fine after re-docking, it's just the mouse that freezes.
There's no other issue with using the mouse, no intermittent freezing; it's entirely reproducible with re-docking.
The only way I've been able to get my mouse responding again is to soft restart Windows (using keyboard to navigate to start button).
I did try unplugging the mouse and plugging it into another port while in the frozen state, but this didn't fix it.