Comment 9 for bug 977438

Can confirm that for me it was caused by the clock on the top pager updating while using the place compiz plugin, for now have removed the clock (<special>+<alt>+rightclick remove from panel), that's stopped it popping up. I think the problem is with place plugin though and there's a bug report here https://bugs.launchpad.net/compiz-core/+bug/976032.

As for the turns-out-to-be-unrelated windows moving themselves about/jumping to the top of the screen thing that I was having that was caused by wobbly windows plugin which has a snap feature by default set to <shift> changed to <disabled> to stop.