I can confirm there seems to have been a change in behavior between 2011 & 2011.5 in this respect. This is probably due to the incorporation of the ViewCube, although disabling the ViewCube doesn't change it back. The documented behavior AFAIK always was defined as followed
When an SRT manipulator is active, you can open a context menu by right-clicking on the manipulator in a 3D view
(the SI2011SP1 User's Guide), which hasn't changed. Seems to me right-clicking outside of the manipulator to get to the context menu could just have been a side-effect, not so much an intended feature. I could however be wrong (and often am...)Apparently I have fallen into the age-old trap of "has been answered elsewhere also already"...