Problem Camcorder/Webcam functions with AMCap but not GoToMeeting or Camtasia?

I've been enjoying tinkering around with adding video input from a camcorder using a Diamond VC500 device (RCA out from camera to USB). With the bundled Diamond capture software it works just fine. With AMCap software it works just fine. With Open Broadcaster Software (OBS) it works just fine.

But when I try to use it with my two most commonly-used tools, GoToMeeting or Camtasia, the source is recognized (Conexant Polaris Video Capture), a signal is detected (according to the webcam properties dialog), but I get a variety of error messages, such as "Unable to initialize the camera", "The camera may be in use by another application", "An unexpected error has occurred. Capture cannot be started."

I just don't know enough about what could be causing this problem. The only related issue I came across was an odd driver naming overlap, but I believe I worked through that (since I am receiving streaming video with two different capture programs).

Has anybody seen anything remotely like this? Perhaps I am wrong, but I keep thinking this may have to do with "The camera may be in use by another application." Is is possible that there is some sort of interference going on? Where should I look?

Win 7 Home Premium (Svc Pack 1)
Dell XPS 8300
i7-2600 3.4GHz
8 GB RAM
AMD Radeon HD 6800 Series

Camcorder = JVC Everion GZ-EX210AU

As mentioned, using a Diamond VC500 to connect it. Thanks!