We're in the final stages of testing the Vegas update (4.0c) but if you are in need of a fix for the MPEG clamping issue mentioned a few threads back, you can pick up the updated encoder by installing the DVDA update (full or demo version updates MPEG for all SF apps).
get the DVD Architect 1.0c update here:
http://www.sonicfoundry.com/download/step2.asp?DID=445
get the DVD Architect 1.0c update here:
http://www.sonicfoundry.com/download/step2.asp?DID=445