I like to use VirtuabDub and the Dynamic Noise Reduction filter for noisy video. It works fairly well depending on the kind of noise. There is also a Temporal Smoother but use it sparingly as it can produce smearing. Both of these are also available from Mike Crash as a plugin to Vegas. Check out the VASST Vegas Plugins page for a list of all the plugins. Here is a direct link to Mike’s Noise Reduction and Smart Smoother. You use them like any other DirectX plug-in in Vegas.
I must be making some sort of critical error in lighting/exposing, as the interiors I've shot often have noise in the areas that don't get much light. I'm usually opening the f-stop around one stop wider than what the auto iris suggests to let in more light, but I still get a lot of noise in flat areas that aren't receiving direct light. [And that's after knocking down detail to -6/-7 and slamming the detail coring up to +6/+7. I'm in cinegamma / cineV, 24pa].
Ah well, when I get home I'll give these things a shot. I messed around with MB last night, and it is able to really smooth out the noise by diffusing/blurring it; though it changes the overall image drastically.