I have two Condor 1553 cards and the API installed on my NTv4.0 system. When I run testcfg.exe to test both of the cards, the first card works and the second card gives me the following error when trying to initialize the card: 'Dual Port Memory...

To clarify the symptoms: Changing the order of the cards in the PCI slots causes the same error. No matter which card gets installed first; the second one always gets the memory failure.

This is because the motherboard in your system is not properly allocating system memory to the card. You need to contact the manufacturer of your motherboard to find out if there is a way to allocate more memory, or you need to use a different motherboard.