Problem with streaming video using dual display monitors.

I have run into problems with some of my (dental) customers using dual display monitors. Basically, I sell & install small USB (dental) cameras using live video and capture/freeze function. This technique calls for specially designed imaging software applications capable of capturing and storing all images by patient name.
Using a dual monitor permits the live camera (video) to be on monitor 2, while monitor 1 displays a different application. Normally, this technique works fine when using a video card with dual output, or two video cards. Yesterday, I ran into machines with one HDMI output (single video card). The IT guy(s) simply attached a splitter (2 VGA) to deliver the output(s) to the two monitors. The card was an ATI X1300Pro (PCI). The IT guy(s) had put a cover over the on-board vga connector.
When dragging the live (camera) window to monitor 2 it works fine initially. However, when trying to capture/freeze the image, it causes the screen to go white. The application is still there but the live video is no longer available. Could it be because of the single video output with the attached splitter. By the way, the splitter is not powered or amplified. It is just an in-line non-powered splitter.
Appreciate any suggestions or help regarding this matter.
Thanks,
Dick