I’d look for msbuild process(es) to kill before devenv. And make sure vbc really has gone too.
And as the comments say, try using msbuild yourself.
Seeing as I’ve got a Nice Answer badge from this, I feel I should emphasise my comment below: In all the cases where this has happened to me there have been no msbuild or vbc processes to kill. If anyone gave or gives me a +1 because they did find a stuck msbuild or vbc process, please comment that this was the case too.