Could be lack of memory or your external hard-drive might have somrthing to do with it.
Give specs of the hard-drive and also list what you're doing when it quits and what exactly happens when it quits.
What are you doing when it stops responding? Is it always after a certain move? Like if you just added an FX or something. Is it random? Granted you're not rich on RAM, but...
I Start Vegas 4, open a project ( 30 min. of avi footage) do a bit of previewing, then it stops responding for about 30 secs, then it continues for a few seconds, then it stops etc
I'd suggest that if you're serious about DV editing you get yourself another 512 Megs of RAM.
Also, is this project on the internal hard-drive, or external?
If external, did you try copying the project to the internal and try running it from there?
I've had the exact same problem with VV3 for a long time and I finally got rid of my external FW drive. Everything works fine using the drive internally. In general, my feelings are that FW drives are junk and not designed for heavy-duty use. Even outside of VV the drive would give me problems with delayed write errors or random disconnects. All this on Win XP Pro with 512Mb of DDR RAM.
Thanks to all of you for your feedback. Yesterday I did some editing on the internal drive only and it worked smoothly, guess the firewire drive is to blame for the misbehaviour.
I've had these symptoms with external drives, but mine are USB 2 as well as firewire, and using the USB connection removes the problem. It seems the extra speed helps get past whatever was causing the pausing.
Haven't tried it, but someone posted that after pressing F5 to redraw the audio peaks, their problem disappeared - sounds worth a try!