I was having some trouble with a new solution, I had added a few NuGet packages to various projects, and everything was working. I checked it into TFS and asked a colleague to review the code.
He got the code out of TFS and tried to run it, but ran into some problems, because not all of the NuGet packages had been restored. I had enabled the “Restore NuGet Packages on build” option, so I was a bit stumped.
After some investigation I discovered the problem. I had checked in the packages folder in the route of the solution. This obviously becomes write-protected, and interferes with the package restore. I closed the solution, removed the packages folder from source control, and reopened the solution and rebuilt. All the packages were downloaded and the solution ran without issue.