Comment 28 for bug 989477

I think I'm having the same problem, in 12.10. Here's how I produce the bug:

-Turn on autohide using Settings-->Appearance-->Behavior

At this point the launcher hides and appears as expected

-Run CompizVonfig Settings Manager, go to Window Management and uncheck "Snapping Windows" to turn the feature off.

At this point the launcher will not appear in response to the mouse. Super and Alt+F1 will make the launcher appear.

Resetting compiz and unity with dconf-tools puts things back to default, with the launcher capable of being put into autohide: dconf reset -f /org/compiz/

I also keep getting this error in the terminal window, but may be unrelated:

WARN 2013-01-18 16:44:38 unity <unknown>:0 Unable to fetch children: No such interface `org.ayatana.bamf.view' on object at path /org/ayatana/bamf/application0x1d19ac0