I make a lot of calls on the computer through MSN. Lately we have found that the video calls are crackly and struggle with quality, where as if we start voice and video separately it's fine.

They should both use the same resources, right?

If there is anything I've learned while struggling to use webcams over the years its that they really are just a pain. Sometimes the firewall lets them through, sometimes its a no go. Sometimes it a hardware problem, sometimes the connection, sometimes software.