Just the other day we have started to get static instead of music during the first 15 seconds of our opening credits (advert) in our productions. It doesn't happen every time, but just on occasion. Any suggestions would be appreciated.

That's a new one. I can't even begin to imagine what might be causing it.

What delivery format are you using?
Have you tried a different rendering engine?

I would try turning off GPU Acceleration in Vegas just to be sure.

• Close TandemVids
  
• Open Vegas
  
• Options | Preferences | Video
  
• Set "GPU acceleration of video processing" to "Off"
  

This must be a Vegas issue as TandemVids doesn't have anything to do with rendering once it's started. Try removing TandemVids from the equation, opening a completed project that has the issue and rendering it manually.

• In TandemVids, select the Search Tab
  
• Select a customer that rendered with static and click Explore
  
• Close TandemVids
  
• Open their completed project in Vegas by double clicking the "*.veg" file.
  
• Render it using the exact same rendering engine you use for your delivery medium
  

Is the static still present?