NuGet Package restore failed for project Miscellaneous Files: Value cannot be null or an empty string. Parameter name: root. 0 0

Question

I have such error in vs 2012: NuGet Package restore failed for project Miscellaneous Files: Value cannot be null or an empty string. Parameter name: root. 0 0

I see

Answer 1

I got this error by accidentally renaming one of the namespace id attributes inside packages.config file to something else. I was able to track this down by comparing checked in version of packages.config, with my local one. After I corrected the problem, all I had to do is close the packages.config file, rebuild, and the problem was gone.