[Bill Church] "Sounds like you definitely need more RAM allocated to the application while editing, vice rendering. I'd try setting to at least 6000MB, vice 600MB. Should make a big difference."
This is a misconception. You want to actually set the RAM preview LOWER because it is only use for performing a RAM preview via Shift+B and it TAKES AWAY memory from other editing tasks and rendering. I would set the RAM Preview back to it's default (128MB or 256MB).
[Paul Gregory] " I'm using Vegas Pro 10."
Are you using the 64-bit version? and are you using the latest 10.0e Build 738?
I would also try adding the nested veg files one at a time. Vegas has to build audio proxies for each veg file and that takes some time. Also doing them one at a time will let you see if there is any one project that is causing the problem.
Finally, make sure that you open each nested project separately before you import it and clean the media pool so that there are no missing files that aren't being used. This will cause nested imports to fail.
~jr
http://www.johnrofrano.com
http://www.vasst.com 
