These are only troubleshooting steps to assist to try and resolve the issue at hand.
There are two possibilities here: 1) one of the video cards; 2) the system.
Since you state that the cards work fine individually, the issue could be system related. However, can you get the video cards replaced and try, do you have the same issue?
I am responding with:
This is a brand new Dell machine with brand new video cards (which came from Dell too).
I'm a bit confused though. In your previous message it was stated that 2 Radeon cards is not recommended or supported. I really don't want to go through to trouble of sending the graphics cards back to Dell to get another pair of brand new cards of the exact same type. It seems unlikely to me that another pair of the exact same cards would resolve the issue. Nor am I willing to return the PC for this matter.
If this configuration is not supported and won't work, that's fine, I'll just need to get either Dell or VisionTek to refund me for the cards so that I can apply that toward a different set of cards (or one of FireMV cards that you mentioned). But since I've installed the cards, I anticipate difficulty returning them unless I can get a confident statement from you that the claimed configuration won't work.
I feel like this should "just work" if the box claims that it will, and I have already spent several hours working on this problem. I want either you or VisionTek to provide me a sure-fire solution, even if that means that the cards I bought won't support the configuration and I need to exchange them for different cards.