You’ve tried to match the AUDIO Bit-rate in Project Settings – that didn’t work. So, all we are left with is that Vegas is trying to read the audio at a rate that your audio system handle it. You’ve also said that if you re-render this file the audio is correct – yes? Well, you could test the media information using the freebie MediaInfo, run your file trough that and investigate just what CODECs the Audio requires and see if they reside on your PC. NB: DO NOT INSTALL any CODEC packs!
I think the BIG clue here is that once you had prepared the Media, Vegas is good to go.
BTW, had you downloaded this from YouTube?
* Grazie
Video Content Creator and Potter
PC 7 64-bit 16gb * Intel® Core™i7-2600k Quad Core 3.40GHz * 2GB NVIDIA GEFORCE GTX 560 Ti
Cameras: Canon XF300 + PowerShot SX50HS Bridge