Try rebooting the PC and then open Pro project and try to burn it. I have read that other buring apps hijack Pro’s burning drivers. Also make sure no burning apps are running in the background. On your desktop, Click Start>Run and enter msconfig. Choose the Start Up tab at the top and deselect ALL, then apply and restart your PC and try again.
BTW…the .m2v and .wav files that the Media Encoder produces are elementary streams that most DVD authoring app want as assets.