Hi Here are some more clues about this bug and a valgrind error log.
The crash also appears when compositing is turned off. It also seems to be connected with my GNOME panel configuration. My left screen has a panel on the bottom with a "Window list" and "Expand" enabled. My right screen also has a panel on the bottom with a "Window list" and "Expand" disabled. If I enable "Expand" on the right panel, Metacity will no longer crash. Also in addition to the window moving from one screen to the other there must already be windows on both screens in order for Metacity to crash. Thanks Tomaž Šolc
metacity.valgrind.gz
Description: GNU Zip compressed data
