I ran 'xdpyinfo -queryExt' in the session where gnome-panel failed to load and the extension which I think it fails on is 'MIT-SHM' which has (opscode: 130, base event: 65, base error: 128)
I ran 'xdpyinfo -queryExt' in the session where gnome-panel failed to load and the extension which I think it fails on is 'MIT-SHM' which has (opscode: 130, base event: 65, base error: 128)