I ran into an interesting issue the other day, I have a client with Dell AIO (all-in-one) desktops. Each one has a dual monitor configuration and they’re running Lync 2013. In Lync 2013->Tools->Video Device Settings you can see the webcam video fine. However when you attempt to share your video it gets stuck on “Loading” forever and never displays the video. If you just start the video, it just shows a blank or grey box. I tried several things, swapping video drivers, updating the webcam driver, disabling other webcam related management applications, but nothing helped. I noticed that not only were there two monitors, there were two video cards, an Intel HD and an AMD Radeon. When I would disable one in device manager video would work but the second monitor was disabled. The same effect occurred when I disabled the other video card and re-enabled the first. In the end, the quick fix turned out to be the disabling of hardware acceleration in Microsoft Office. This is easiest found in Microsoft Word options.
This can also be disabled via Outlook or via the following registry key:
DWORD: DisableHardwareAcceleration = 1
For more information, check out the following support article: http://support.microsoft.com/kb/2761977