I wanted to render an older project that I opened in version11 and when I select any render option besides Sony mxf the Render button on the bottom is grayed out. Why can't I select mpg2 to render to? I never had this problem in version 9.
Just a guess, if you have no render template selected the Render button will be grayed out. Do you have "Show Favorites Only" ticked? If so, untick it and select another template like your Mpeg2. Once you highlight it (selected) the button should then be active.
I did select/highlight the mpeg2 template and the Render button turns gray as it does with many of the other options. For some reason the button is active when I select any of the Sony mfx templates which comes up as the default when I select Render As in the File menu of Vegas.
Very odd.
At a guess it sounds like you have ran into the "i cant import older projects into v11" thing. If you start a new clear project then add a clip, can you render out to mpeg2? If so, then that would confirm it.