I upgraded my system to win7/8GB RAM and Vegas 9c 64bit/32bit. It keeps crashing when rendering simple HD projects using Sony AVC or MainConcept AVC templates. Here's error message when rendering in 32bit version:

Problem Description
Application Name: Vegas Pro
Application Version: Version 9.0c (Build 896)
Problem: Unmanaged Exception (0xc0000005)
Fault Module: C:\Program Files (x86)\Sony\Vegas Pro 9.0\FileIO Plug-Ins\mcmp4plug2\mc_enc_avc.001
Fault Address: 0x5C74AD03
Fault Offset: 0x0007AD03

Fault Process Details
Process Path: C:\Program Files (x86)\Sony\Vegas Pro 9.0\vegas90.exe
Process Version: Version 9.0c (Build 896)
Process Description: Vegas Pro
Process Image Date: 2009-10-26 (Mon Oct 26) 16:41:04

and here is another one:

Problem Description
Application Name: Vegas Pro
Application Version: Version 9.0c (Build 895) 64-bit
Problem: Unmanaged Exception (0xc0000005)
Fault Module: C:\Program Files\Sony\Vegas Pro 9.0\FileIO Plug-Ins\mp4plug2\sony4vem.dll
Fault Address: 0x000000000356BCC3
Fault Offset: 0x000000000001BCC3

Fault Process Details
Process Path: C:\Program Files\Sony\Vegas Pro 9.0\x86\FileIOSurrogate.exe
Process Version: Version 1.0 (Build 8)
Process Description: File I/O surrogate (not visible)
Process Image Date: 2009-10-26 (Mon Oct 26) 16:33:34


What is going on???

Could you post a screen shot of your render settings.

it is a sony avc template - nothing changed

Just a guess, but check that your output settings are of a LOWER bitrate than your source video. Also try changing system settings to MPG2 rather than MP4 just to see if it works then.

that's the point - it only crashes when rendering to Sony AVC or MainConcept AVC TEMPLATES are selected - never when to MPEG2. Yes, I use lower bit rate of 14MBs to fit 3.5 hours of video on BD.
Why I must use AVC:
I noticed that most of my customers have problems playing BD rendered to MPEG2 25MBs (most players will stutter or freeze towards the end of BD when laser must read outer portion of the disc) it just can't handle such a huge volume of information; it will never happened when compressed to AVC (I guess due to much lower volume of data - 15MBs). It is not a new problem - same "rules" of handling amount of data apply to regular DVDs (therefore I NEVER render regular DVD with bit rate of more than 6500000 although in theory it could handle 8000000).