I've had it! I searched the forums here and elsewhere and tried everything I've seen so far.

When I render the SD version, everything is fine and dandy. When I render HDV, it dies. It got a little further this time though at about 50 minutes in length on a 1 hour 15 minute project.

I'm rendering out to the basic HDV 1080i template.

All clips captured in Vegas.

Preview Ram set to 128 MB - Processor Threads to 2 (Dual Core proc.) and all unneccessary processes have been halted prior to rendering. "No recompression if not needed" has been disabled...

Before I changed preview ram and "No recompression if not needed" , I got an error that was:
EventType : BEX P1 : vegas80.exe P2 : 8.0.0.179 P3 : 470e74b9
P4 : mcplug.dll P5 : 2.0.0.3994 P6 : 470e726d P7 : 000412ad
P8 : c0000409 P9 : 00000000

So I changed the preview ram and disabled the no recompression and NOW, I'm just getting a "Vegas has encountered an unexpected error and needs to close." error message.....

TIA!