I am developing a VSIX project in VS2013. My current project is a little bit detailed but today I realized that error happens even on a new project.
To find out reason of the problem, I have created a very simple VSIX extension. I just opened new project window and selected Extensibility and then VSIX. After project creation I built project and received this error:
C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v12.0\VSSDK\Microsoft.VsSDK.targets(503,5): error VSSDK1040: There was a problem enabling the extension with a VSIX identifier of "0.0.1". The input source is not correctly formatted.