Did they change that on 4R6 I can no longer unmask all with Ctl + shift + A
Currently Ctrl+Shift+A will select all your mesh topologicaly. So if you just select some polygons from a mesh with several topological separate parts you will notice it will select all your entire part. This is extreme handy when creating panel loops and other tricks
To mask all you can just Ctrl+click on the canvas (outside the model in the document) To inverse just click again.
Hope this helps
You can reset the shortcut if you wish. Ctrl+Alt+click on the Tool>Masking>Clear button and then press the hotkey. But remember that there will then be no hotkey for the Tool>Visibility>Grow All button (though you could assign something else to that).