If you weren't confused before...
This is only affecting Outlook. I ran detect and repair and nothing changed.
You know how windows memorizes your preferred windows size? Well, for some reason, I think that the standard window sized got reduced to zero, so there is nothing visible to resize.
I use a program called UltraMon so I can easily move windows back and forth between two different monitors set at two different resolutions. It has a great feature called "relative sizing", so that if a window takes up much of the screen on my higher resolution monitor, when I move it to a lower resolution monitor, it automatically resizes the window to look 'relatively' the same. In this case, it won't be larger than the second monitor.
I think what may have happened is that I had the window extremely small in my higher resolution monitor, and perhaps when I moved it to the lower resolution monitor it completely disappeared. I'm not sure how this is possible because any other windows, when this happens, no matter how small it becomes the title bar tools are always there. As an experiment right now I made an IE window really small and flipped it back and forth from monitor to monitor. It eventually gets smaller and smaller but still the title tools are there and the title bar is re-sizable.
I also thought that maybe it is resized but just way off the screen? I have reset my monitors to the largest resolutions I can, and still I don't see Outlook. Could it be even further off the screen? Beyond what my resolutions can see?