Have you checked the system requirements for the card? Many are win-cards that use Windows APIs to do some of the work for them, and require a certain speed processor to keep up...
Also, have you uninstalled the software and drivers, rebooted, then reinstalled? That frequently helps with problems. Check the installation instructions for the card- some need the drivers installed before the software, some need the software before the drivers, and others really don't care but specify a preferred method.
Hope this helps. BTW- Welcome to Techspot!