This message could help:
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x3c0021f (Debug - Ma)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
When i run "metacity --replace --display=:0" and the screen freeze again this message is shown.
This message could help: activate called by a pager with a 0 timestamp; the pager needs to be fixed.
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x3c0021f (Debug - Ma)
Window manager warning: meta_window_
When i run "metacity --replace --display=:0" and the screen freeze again this message is shown.