Spaces/Dock (+Firefox?) problem

My problem: Spaces and Dock suddenly stop working. Only the current space is active and no other is accessible (via any means: e.g. cmd+tab, ctrl+arrows, going to one of the corners with the mouse, going to the spaces icon on the top bar...). If I open an application that is bound to a particular space, it will open but I can't access it. The same happens to the Dock: it just stops working (in my case stops popping up when I go down).

It's happened to me twice in the past few days and both of the times I was the space where Firefox was running.

Please help! It's annoying because if I have a document open in another space, I can't go there and save it before the restart of the computer (apparently the only possible solution). It reminds of the old windows time, too bad.

 

thanks for the tips. i'll try it out. by the way, do you have any idea why that should work? (i see the logic behind dis/enabling the spaces but why changing the numbers?)

 

by the way, i forgot to mention that once this happens, "restart" actually doesn't work, i had to switch the computer off by pressing the start-button.

i'll be back with details if it happens again. btw. is there a way to "report a bug" to apple?