How much HD space have?
How much of it is defragged?
Have you looked in your Vegas Temp directory? See if you have old mouldy *.tmp and "other" files lurking?
Do you render To your HD?
I also notice that you have at least 3 FXs on unrendered NTSC footage? Is your footage NTSC - your Project is set so? And on top of that you are rendering to WMV? Now, in all fairness to Vegas Plat - you DO have Vegas Plat - it WILL do all of this you are asking. However, the more constipated a system becomes, then the more difficult it is to "squeeze" your masterpiece OUT!
So, check out the condition of your HD C: drive and get back to us. If you working as close to the bone with your CACHING - this is used for rendering - then you/we can have issues.
Grazie