I keep getting this error while trying to add a project under a folder in blank solution using Microsoft visual studio 2005. I did not use any character like .? etc in filename but still got the error until i just figured out that the directory path of project contained & character.e.g my project had a directory path C:\My Projects & research\myproject\ where directory My Projects & research contained '&' sign.
I changed directory path to MyprojectsandResearch and it worked fine.I also changed name of file to myprojects.objects and did not give me any error. so the Error was generating from path and not by filename.I think it is some kind of bug in Visual studio 2005.