The unity-panel-service crashes with a bunch of segfaults in syslog. It then respawns, then crashes again.
The visible symptom is that applications that use the global menu "flicker" because the panel "swallows" the menu when running, then crashes and sends the menu back to the application itself.
Some applications, such as gnome-terminal, start "shrinking" from this behavior and eventually become unusable. This is because when the menu is swallowed, the window gets reduced vertically, and when the menu returns to it, the app doesn't resize back up to accomodate it.
Other apps, such as Firefox, just flicker uncontrollably.
This happens on a fresh and fully-updated Oneiric system (as of 2011-07-13).
I'm reporting this on a Toshiba Tecra S11 with Intel video but I've seen it happen on several other machines; some, though, don't exhibit this problem and I haven't seen it on a virtual machine. If necessary or helpful I can compile a list of systems on which it happens.
DistroRelease: Ubuntu 11.10
Package: unity-services 4.2.0-0ubuntu3
ProcVersionSignature: Ubuntu 3.0.0-5.6-generic 3.0.0-rc7
Uname: Linux 3.0.0-5-generic i686
Date: Wed Jul 13 16:38:37 2011
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Alpha i386 (20110705.1)
raise () from /lib/i386-linux-gnu/libc.so.6
abort () from /lib/i386-linux-gnu/libc.so.6
g_assertion_message () from /lib/i386-linux-gnu/libglib-2.0.so.0
g_assertion_message_expr () from /lib/i386-linux-gnu/libglib-2.0.so.0
Title: unity-panel-service crashed with SIGABRT in __kernel_vsyscall()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare