If you use them on different machines, I'd say yes. Every attempt that I've made to get a capture card to working while there is another video card in the machine has resulted in failure. I've read that in order for capture to work properly (This was on my ATI All-in-wonder-pro) it had to be the only card in the machine.
If you do get it to work, please post what hardware you used and how you did it.
Good luck