Color 1.5 video output displays erratically

This is a very simple but frustrating problem:

I'm new to Color and just learning the basics of grading. I've been able to use the program without any issues for a few weeks now, but just in the last few days, my external monitor is no longer outputting video. I work in an edit house where lots of different people use the machines, so maybe it's a settings thing?

I'm working with Apple ProRes 422 (HQ) 720p media. The sequence displays properly out of FCP but once I import into Color, the screen goes black. We have a blackmagic box installed, so its not a firewire issue.

I've tried about every single video output option on the list to no avail.

The other strange thing is that the external monitor will output the image (erratically) when I'm in a secondary room and have a grade "enabled".

But most of the time, when I'm in a primary room, or in a secondary room with the grade "disabled" there is no video output on my external monitor.

Your advice would be so very much appreciated!