Description of problem:
Due to issues with the R300 Gallium driver, I have rebuilt mesa-7.10-0.29.fc15 without the R300 Gallium driver, thus using the standard R300 TCL DRI2 driver.
However, in this case, gnome-shell does not work properly. The shell appears as expected, but when clicking "Activities" in the panel then it disappears, and the following error message is appended to .xsession-errors:

----------------------------------------------------------------------------
 (nm-applet:1662): libnotify-WARNING **: Failed to connect to proxy
 Window manager warning: Log level 32: Failed to load module "pk-gtk-module"
 ** Message: applet now embedded in the notification area
radeonSetSpanFunctions: bad format: 0x0002
radeonSetSpanFunctions: bad format: 0x0002
** Message: applet now removed from the notification area
gnome-shell-calendar-server[1892]: Got HUP on stdin - exiting
Gtk-Message: Failed to load module "pk-gtk-module"
      JS LOG: Cannot create "Network" item, .desktop file not found or corrupt.
      JS LOG: GNOME Shell started at Sat Mar 19 2011 15:26:08 GMT+0100 (CET)
GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: Method "GetServerInformation" with signature "" on interface "org.freedesktop.Notifications" doesn't exist

** Message: applet now embedded in the notification area
----------------------------------------------------------------------------

The relevant entry appears to be "radeonSetSpanFunctions: bad format: 0x0002".

Version-Release number of selected component (if applicable):
gnome-shell-2.91.91-2.fc15

How reproducible:
Always.

Steps to Reproduce:
1. Start gnome-shell in conjunction with the R300 TCL DRI2 driver.
2. Click panel.
  
Actual results:
Panel disappears for a moment without opening "Activities".

Expected results:
Panel works as expected.

Additional info:
Despite the non-standard use of the R300 TCL DRI2 driver, I think this issue is of general relevance because there is no obvious reason why gnome-shell would require the R300 Gallium driver to work.