Hey Alex,
Not sure if restarting fixed your problem or not, but came across this on the internet – Basically some third party applications you can use to temporarily disable DirectX plugins that may be causing Vegas to crash on startup.
Sam Nicholls, Studio8 Media
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Managing DirectX plug-ins
DirectX plug-ins are registered and have specific path locations written to the registry. For this reason, you should manage DirectX plug-ins using a third-party plug-in manager application. Use one of the plug-in managers listed below to turn off DirectX plug-ins which fail to initialize, or which cause Adobe Audition to freeze at startup. For detailed instructions on how to use the plug-in manager refer to the website listed below and the program’s user guide.
Third-party plug-in management software
DXMan (DirectX plug-in manager)
http://www.analogx.com/contents/download/audio/dxman.htm
VB Plugman (DirectX plug-in manager)
https://perso.wanadoo.fr/vb-audio/us/resources/plugman/vb_plugman.htm