Unable to render in HD

First time poster, long time reader, and thanks to all for your help with previous issues.
Currently I am trying to render a movie I made into HD format.
When I initially made the movie I did it in SD Format to burn to DVD, but I purchased a Blu Ray burner so I can have it in HD.
First time I tried this I changed all project settings and rendered into the default 1920x1080 format using mpeg2 for video.
Burnt to Blu Ray -WOW! Very Happy
2nd time
Opened another previously edited movie, changed the project settings and then try to render into HD but it crashes every time. I have tried to render possibly 20 or 30 times using different settings. I even upgraded to Vegas 11 thinking that may help. No Luck. I can render with the new settings to SD mode, but I cannot render to HD no matter what I do.
I am trying to render video only in Mpeg2 Blu Ray at 1920x1080 50i. I get approx 3 minutes in and it crashes.
Any suggestions appreciated. I am hoping I dont have to redo the movie. It took over a month is 2 hours long and has numerous video, photos and audio in it.