Sony Vegas Pro 10 Crashing to Desktop when loading HD footage

[xX-Towrd01-Xx]

I have just set my HD PVR to record in 720p, and my capture module has no problems with this, and i can load the video fine in Windows media player or other video player on my PC. But for some reason, when i import the footage into Vegas, it has a massive fit of lag, and i cannot open the footage in the trimmer or in the main time line without vegas crashing to desktop with no error messages, nothing.
But when i open my 560p recordings, they work fluidly in vegas with no problems at all, so this is leaving me puzzled as i have little or no idea whats going wrong,
any help would be massively appreciated thanks

[aedipuss]

looks like a laptop in your specs. or a older low performance tower. either way it's not up to the requirements of editing HD video.

[budwzr]

Did you try lowering the bit rate to 5Mbps?

[xX-Towrd01-Xx]

yes i did try lowering the bit rate, and yeah, i think i just need a new PC to edit this footage, i was just confused by that going from 560p to 720 would lower performance so dramatically, guess its just my PC, thanks anyway guys