Well, hoo-rah. After having my faith shaken with Vegas 6.0c, hanging on long renders, using 6.0d I did my first long render today, directly from the timeline to MPEG-2. Went straight through (22 hours with all effects) without a hitch.
Yes DJPadre, I should have added that I'm running an "old" Dell P4 with no HT, a 2.53gHz with 'only' 512 RAM. And the computer is loaded down with all sorts of other software. But the key was that with all else remaining the same, the only change was the 6.0d update and that seems to have done the trick. Now I can uninstall V5 and carry on.
And P.S. the timeline render was from 92 minutes of nested projects.