Keep Calm, same problem here with the ^ on the google homepage using Opera.
Didn´t show notifications or Apps on the Pc (Maybe are invisible) cause de ^ is part of the notifications and apps window frame.
I cleanned cookies/Historial several times and reinstalled Opera and nothing changed, so it´s not a virus, it´s a bug. Firefox, Chrome and IE showed the notifications menu properly for me.
For the moment, you can see your notifications accessing directly to G+ via browser, on the main panel on G+ site. An still can access manualy to apps via browser.