Comment 32 for bug 563100

This is a known bug in Xorg 1.7.

https://bugs.freedesktop.org/show_bug.cgi?id=24986

We did investigate this about a month ago, until we discovered that it was a bug in X. At the time, it did reproduce in Debian unstable, though the bug report here suggests that it currently does not. The freedesktop.org bug report lists an available patch, so it's possible that Debian unstable has applied this patch or their own. It's also possible that the server layout that the original poster tested with in Debian unstable is different: this bug only reproduces when screens with a higher ID are placed to the left of screens with a lower one.