I am new, but the solutions I have heard so far have been these:
Reboot Vegas, to defrag the swap file, and also to kill any additional instances of Vegas running in the background.
Make sure project properties are the same as render properties.
Kill all Antivirus and Internet Security before starting a render (as you won’t be going online during that time).
In Options > Preferences, set Dynamic RAM Preview to 0. Set number of rendering threads to 1.
If that does not work, please let us know your project properties, and your rendering qualities (including audio).
I hope that helps.
Norman Willis
http://www.nazareneisrael.org
servant@nazareneisrael.org