Additional buttons unavailable in the button editor of reference monitor in Premiere Pro CS6

Hi.

I have been unable to get a response from the Adobe community on a problem I have started experiencing, so I thought I may be able to get help from this community.

Running PP CS6 PC platform. For some reason I am unable to add any additional buttons at the bottom of the reference monitor except the "Go to Next/Go to Previous" and "Step Back/Step Forward" buttons. When I hit the "+" no other buttons are available to add, including the Play button (see images). I have tried most of the basic troubleshooting steps recommended on the Adobe forum, including resetting deleting the preferences file and the ICC profiles.

Oddly enough I started having the dreaded "Rendering Required Files" issue as well, and my Workspace layout was reset. I tried to search Google for a solution to this issue but came up with nothing. Funny enough, the search came back with articles related to the "Rendering Required Files" issue. Are these problems related?

Please help, I am working on a fairly large multi-camera project with an "involved" timeline. The current project sequence is just under an hour and I am in the process of cutting it down to less than 30 minutes.

Any help or point in the right direction would be greatly appreciated.