Set your project properties to the frame size and rate of the video, in this case 1280 x 720 @ 30 fps. Or you can let Vegas make these settings by using the match media (or whatever it’s called) in the top right of the project properties window.
Render using the Sony AVC template with the same numbers.
If you are using a lot of filters turn off the filtered view using the split screen view (select all) in the preview window. Your filters will still be there when you render and the viewing will be less choppy. Otherwise you need a faster processor to handle the workload.
Jeff
2-Xeon X5680 @ 3.33, EVGA SR-2 Mobo, 48GB DDR3, GTX 580 3072MB, 16TB Attached Storage, Win7, Vegas 11 x64