I've never seen this myself, but there can be two reasons:
1) zeitgeist-daemon is not running - in this case you should be able
to see some messages about this on stdout if you run the apps place
daemon manually
2) It's a bug in Unity's rendering layer - in this case you need
someone from the shell team to track it down
I've never seen this myself, but there can be two reasons:
1) zeitgeist-daemon is not running - in this case you should be able
to see some messages about this on stdout if you run the apps place
daemon manually
2) It's a bug in Unity's rendering layer - in this case you need
someone from the shell team to track it down