Video Output to TV is shutting down on full speed playback of video, or split screen display
Assuming that everything worked fine before you replaced the video card, did the software vendor recommend a video card for this set up? if not, does the software vendor provide a list of supported video cards? Does your new card fall in this list?

I highly suspect that the replacement card has a compatibility issue with the "capture" software. Have you contacted technical support for the software vendor?

It is possible there is also a driver conflict or that when you replaced the video card you did not provide the correct driver. Assuming this is a PC running Windows, did you check the 'device manager' to see if there are any yellow or red flags?

How to check the device manager, one way. Start-->right click on 'my computer', then choose 'manage' from the drop down menu, a 2 pane window will appear, click on device manager in the left pane, look for details in the right pane.