Comment 10 for bug 872207

This has been a problem since Natty. I reported it in Bug #796897 which has just been marked as a duplicate of this one. As mentioned above it's some kind of issue with how compiz is giving focus to windows. (Some things are better in Oneiric - for example, in Natty I used to have the problem that the only way to give focus to the Contact List window in Empathy was to use the Alt-Tab switcher, but this is no longer a problem.)
I can't reproduce it every time I use Ctrl+Alt+Arrows and haven't figured out what triggers it exactly. Using the Unity launcher panel to select a window avoids the problem, but on a netbook with a trackpad and no mouse it's much easier to use the keyboard, and I keep Firefox maximised in its own workspace, so I see this at least a few times per day.