In a nutshell, I've used Vegas since version 7 and upgraded all the way through the most recent version of 9.c. I've used the exact same workflow for years, editing weddings in HD (m2t format) of 1.5 to 2 hrs in length. Recently, on a project in Vegas 9c, I worked my way through an hour of complete edited footage applied MBL effects. Then in the last 3rd of the project Vegas started freezing and had to manually shut down. To make a long story short, I get the same results of Vegas (not responding) I've done all I can think of including:
moved source files to different drive
moved project file to different drive
recaptured source files (on original drive and new drive)
restored factory settings on computer
talked w/ Sony IT and went through all troubleshooting
clean uninstall/reinstall of Vegas 9
started entire project from scratch
had an IT guy check my computer, found nothing wrong or out of the ordinary

One of my editors was able to cut the project and get it almost done on his computer, but that doesn't help me in the long run. I've edited other projects with my computer since with no issues, but this particular project still freezes. I'm probably leaving out some of the things I've tried so forgive me. This is been going on for over a month and now it's getting to close to the deadline for the project. Any thoughts would be appreciated.

When it freezes, is there a pattern of what you're doing right before it freezes? FOr me, it freezes quite often, and most of the time, it's when I'm scrubbing the timeline..

However, it's not a permanent freeze as it will usually come back to life after 30 seconds - 1 minute CONSISTENTLY each time.

I'm trying to figure out if it's an issue caused by my OWC Qx2 RAID tower or the Rosewill ESATA card I'm using.

It has froze right after it loads the project and I don't touch a thing. It froze while scrubbing, once it froze when I cut a clip. Really no rhyme or reason to this issue. I thought it might be a bad clip so that's why I captured it again. I have noticed outside this issue that Vegas 9 does freeze quite often like you described. I've experienced that with a variety of different drive setups.

Are you viewing content to an External Monitor using a firewire connection?

Grazie