I've had this happen once, so I thought I would post about it. I entered full screen mode and my input was captured. Then I used cmd-return to return to windowed mode and I could not get out of grabbed mode! I diligently kept trying different gyrations until the status bar showed I was out.
I have been unable to reproduce this again but I thought I would log it.
Anyway, to answer the original question, to ungrab the key combo to use on the Mac is Control-Command (which is positionally equivalent to Ctrl-Alt on the other platforms, so you can use your keyboard muscle memory).
Normally, this tip is displayed in the status bar when you are grabbed. Did you hide the status bar by any chance? Or was the status bar shown and yet you didn't see the tip? Please let us know what happened so we can improve the discoverability of Fusion. Thanks!
Thanks I know the ungrab sequence-- I type it unconsciously by now.
My original problem sequence was:
1. Windowed mode, choose View > Toggle Full Screen mode from menu
2. Click in full screen mode (no dialog warning, or tool tip, or pin-ribbon is visible)
3. Type Cmd-Enter to toggle out of Full Screen mode back to Windowed mode
4. Try several times to register Ctrl-Alt to get out of grabbed mode.
NOT reproducible easily
One trick that's worked for me in the past to get out of input-grabbed mode was to pick up my Apple Remote and launch Front Row, and then exit it. It gives me my dock back, as well as the Fusion pull-down menu.
I am not sure it's supposed to do that, but it is kinda handy.