Successful Vegas Pro Workflow
 

I recently rented a 5DMII and shot some footage, unknown to me was the horror awaiting me in the editing room. First I loaded the raw footage into Vegas Pro 8c which was not editable, I then tried CineForm Neo Scene which seemed to work like a dream at first however conversion took a few hours and chewed up 86Gb. I edited my project using CineForm and all was well until I tried my first render, it failed miserably, I was unable to get a out a full render after two days of Vegas crashing hell, finally I decided to break my render up into pieces and stitch them together however there was small gaps between the parts that Vegas could not eliminate, so once again I failed.

My final solution before utterly giving up was to use Grass Valley Pro Coder 3, using Pro Coder I converted my 5DMII footage to HDV 25P which Vegas handles very well and mixes perfectly with my XHA1. This didn't take too long and only used 7Gb of space compared to CineForm's 86Gb!! CineForm is a lossless codec, for my work HDV is all I need. Vegas rendering is stable without any crashes now. Pro Coder will set your bank balance back quite a bit however is worth the money, my Intel Quad Core Q6600, 8Gb DDR800, 2TB Raid 0, Geforce 9800GT was unable to cope with CineForm.

Strange. My computer is spec'd much below yours and runs the 5D->Cineform->Vegas 8 workflow perfectly. No crashing. Mine actually will edit the raw 5D files in Vegas, but only with a display of about 4-8fps.

Maybe it's a hardware issue with your computer?