I just changed my startup setting from 0 to 2 because I do not ever need a blank "Drawing 1" to work off of. Now I am wondering if that screwed something up because when I boot up AutoCAD and immediately try to open a Sheet Set, I receive the attached messages and then AutoCAD crashes. Is this a bug that needs to be fixed? Has anyone elese had this issue?
I'm in 2013, wonder what's the deal. Maybe that's why the default setting in 2013 is to make that obnoxious "Drawing 1" everytime you start the program, so that you don't crash when opening a sheet set right off the bat?
I experience the same issue, but I haven't yet connected it to having no drawing open.
I have found that if I open any dwg file without using Sheet Set Manager, then close the drawing, I can then use Sheet Set Manager without errors (even with no drawing open).
Like you, I do also start AutoCAD with no blank drawing. Although this is clearly a bug, changing that setting back to the default of opening a blank drawing on startup might be the simplest workaround.
Like a lot of other dumb little bugs that popped up in 2012 and continue in 2013, I have little faith that AutoDesk will fix this one either.