PC cannot be woken if it sleeps while MM is controlling another PC

[Heusos]

Two PC's side-by side, call them A and B.
A has a mouse and keyboard set using MM to control A or B.
Set the mouse pointer on the screen of B.
After a timeout, A sleeps.
It is impossible to wake it because the mouse and keyboard are redirected to B.
B cannot be controlled either, because A is sleeping.
Version is 2.2.1.0327

[bralexc]

I've had this happen on me so many times but could never pinpoint the root cause. Also noticed this only happened when my my 'A' computer, a desktop with 2 monitors, only showed the problem when one of the monitors was not connected.