Comment 13 for bug 737891

Andres, can you confirm that this happens when booted into Classic Desktop (no effects)? It appears from your bug report that compiz (or kwin compositing) is turned off, but I want to be doubly sure this is true.

The reason is that upstream says that this bug is because there is a 4096x4096 maximum texture hardware limitation for compositing with this Arrandale chip. So you either need to disable compositing, or arrange your screens to not exceed this limit.

From your log files it appears your laptop is 1280x800 and you have a 3840x1080 monitor, which totals to 5120, and since that's larger than 4096 the graphics card can't handle it.

(Is this correct, that you have a 3840x1080 monitor?)

A way to work around this limitation would be to have your laptop monitor positioned above or below your external monitor.