I'm noticing behavior in Firefox 17 where all the glass can be used as a drag handle when the menu bar is disabled. However, when the menu bar is enabled, only the window title glass can be used as a drag handle. The glass surrounding the menu bar and the tabs don't respond to mouse dragging.
There is a bug report 667234 regarding this issue for Thunderbird which has been addressed (IIRC), but it also applies to Firefox.
Slashdot Mirror
I'm noticing behavior in Firefox 17 where all the glass can be used as a drag handle when the menu bar is disabled. However, when the menu bar is enabled, only the window title glass can be used as a drag handle. The glass surrounding the menu bar and the tabs don't respond to mouse dragging.
There is a bug report 667234 regarding this issue for Thunderbird which has been addressed (IIRC), but it also applies to Firefox.