I'm running Kubuntu (the KDE desktop flavour of Ubuntu) and use the Kicker menu bar to launch applications. Because I use my beloved Thinkpad X40 almost all the time, with its dinky little 1024x768 display, I need as much of the screen real-estate as I can get my hands on. To this end the menu bar is configured to auto-hide when not in use, and re-appear when I drag the mouse pointer to the bottom of the display.

So far so good.

Just occasionally, however, it refuses to pop back up. Once it has done this, it never comes back; logging out, or even rebooting have no effect. It's lost.

One solution is to trash my ~/.kde directory containing the settings for all KDE applications (including Kicker). That fixes the problem (until the next time) but it means I lose all my other options.

Another solution is to delete the ~/.kde/share/config/kickerrc configuration file. That's better, but loses other changes to Kicker itself, which may not be all that desirable.

Last time it died I tracked it down to a single line within the configuration file. For some mystifying reason the XineramaScreen property is being reset from its initial working value of 0 to a non-working value of -1. A relatively non-destructive fix is therefore to replace this line in kickerrc: XineramaScreen=-1 with this line XineramaScreen=0 and then restarting the kicker process.

I still don't know what the root cause of this change is, but it looks like it's this bug: "Bug 118551: Autohide toolbar disappears completely."

Incidentally I used to get a very similar problem on Windows (NT 3.51 through to XP) where I accidentally dragged the top of the menu bar down to the bottom of the screen, effectively resizing it to be invisibly high! That was self inflicted, though, and could be fixed by dragging it back up, whereas as far as I know the Kicker problem materializes of its own accord.