Just want to add onto Lange's post about project properties...
If the project property differs from the video being worked on and exported, you'll end up with frame blending (compare frame by frame of before input to output) . As far as I know, it was default behavior for vegas 9/10.
You can click the button to the right of [save][X] to have Vegas match project to file property.
and about exporting...
If you want to export using lagarith's lossless codec (vs uncompressed), you can compress it down using virtualdub & x264.