Try using a hardware solution like a camcorder hooked up via firewire (DV), or a Canopus ADVC300 hooked up via firewire for output to a monitor. There are better, more expensive solutions, but these work too. I tried Scopo Gigio but found it to be quite buggy.
Good luck!
https://www.youtube.com/graphicsdump
https://www.myr3d.com