My site action menu was having problems. The menu was dropping down; however when I clicked the links nothing happened. I was having the same issue with modifying the site settings – basically very few links work. They are all visible but didn’t open when I click on them – nothing happened.
After a bit of Googling found some posts suggesting that disabling “DivX Plus Web Player” does the trick.
Tried it :-
Tools –> Internet Options
Programs Tab –> Manage Add-ons
Find “DivX Plus Web Player HTML5 <video>” and disable it
Site Actions menu clicks now work.