grey/blue overlay over sessions - keyboard works but mouse does not. Windows above RDM transparent.

I've had this before and restart of application solves it but im keen to find out what key combination I've accidentally hit to do this and what if anything i can do other than restarting the application to fix it.

Other windows dragged over the top of the RDM Session are also transparent - i can see the RDM window behind them.

I can interract with the session tabs ie right click > logoff works but cant click on the Yes to confirm logoff though keyboard (tab > return) works fine.

Sure its something simple but searching the forum has not thrown up anything obvious.

Cheers, Tom