I've rendered hundreds of videos without problem. A couple of weeks ago I had a problem where my rendered audio (I render out an AC3 and a mpg for DVDA importing) just died part of the way through.
I have tried EVERYTHING. I've tried two different computers, I've tried rendering to different folders, I've tried naming the files differently. I've tried copying and pasting the project into a new, fresh project file. I tried to render wmv for the hell of it...also broken.
I sort of gave up on it for a while, and worked on other projects instead.
Today, it happened again, and I've been trying a ton of different things today, but still nothing is working.
Do ALL your PCs have plenty of free space to render? If this ISN'T the case then do some housekeeping. If you DO, then you've got to be looking at more hardware issues, like over-heating and potential PSU failings. But to have this occurring on other machines too? Seems unlikely.
You've tried WMV, how about starting over with plain simple AVI Media matched to a Project. If that doesn't work then IMO you've got to be looking at something more fundamental, across ALL the PCs.
Bottom line, Vegas is working here and yesterday I've also rendered to AC3, but I'll recheck. However, this is so a regular workflow for many Users that is have thought there'd have clamouring on the Forums by now.
Video Content Creator and Potter
PC 7 64-bit 16gb * Intel® Core™i7-2600k Quad Core 3.40GHz * 2GB NVIDIA GEFORCE GTX 560 Ti
Cameras: Canon XF300 + PowerShot SX50HS Bridge