My vegas has been crashing a lot lately, to the point that I almost uninstalled it and deleted all my projects. But after some research, I figured out that there are certain steps that can be taken in order to reduce, if not stop, the constant crashing.
1) Keep your registry clean. A lot of mess gets cluttered in the registry due to crashes/failed render attempts etc, which further aggravate the problem. Make sure to download/buy a good registry cleaner and run it once every week.
2) The dynamic RAM preview feature is an important key to solving this issue to a great extent. This is the one that ultimately worked for me. Go to Options > Preferences > Click on the Video tab > Reduce your dynamic RAM preview to 16 MB > Apply. By default, your RAM preview is set to 512 MB which is insanely high. It eats up a lot of the RAM which might cause the crash.
3) If you have an Anti-virus/Malware/Spyware, try disabling it temporarily before rendering. A lot of times Anti-virus softwares interfere with the rendering process.
4) In your Project Media tab, there is a small lightening bolt figure on the top left corner. It basically gets rid of the unused footage. Click on it to clear the clutter and try rendering again.
5) Make sure you aren't running any heavy base process in the background while rendering - Installation of any software, for example. Stall everything until your rendering is done.
6) When you click on 'Render as', next to the 'Template' tab, there is an option called 'Custom', click on it, go the video and change the format to WMV 8 or lower (if you're encoding into WMV) Try rendering again.
Hope these tips helped you, because I know what it feels like to have Vegas crash on you again and again
If you have any more tips, feel free to share.