I use this extension: http://www.apfelquak.de/2010/06/12/maximize-safari-extension/ It adds 4 buttons to the toolbar. The Maximize to Left, Maximize to Right and Maximize Window buttons are still working. The left most button brings up an additional toolbar and clicking on one of those resolution choices no longer functions and the toolbar just goes away without resizing the screen.
Sounds pretty much like bug 114561. *** This bug has been marked as a duplicate of bug 114561 ***