I have a gnome-shell desktop that, since the update from ubuntu 11.10 to 12.04, acts strange. In detail, I have a high CPU activity that seems (looking from other questions here) could be triggered by a theme error.
Now, I have no special theme installed --- but the gnome-tweak-tool is reporting an error (look at the screenshot down here). Given that:

• the theme list is "locked"


• the warning signal is not clickable


• running gnome-tweak-tool in a terminal shows no useful errors


• activating lookingGlass shows no error whatsoever


• .xsession-errors has not errors

Anyone knows where can I see for the specific error, or how to reset the configuration without deleting all the .dconf directory?