One of our teams hit this today with strange errors in the build logs. The errors looked like this:-
$/Development/Source/Service.csproj ('Package' target(s)) - 23 error(s), 0 warning(s), View Log File
There were many of these in the build output. Some head scratching and searching later turned up the answer. Someone had checked in a bin folder to Source Control – this will make it read only etc etc. (You can guess the rest)
Posting here so that next time it gets me I have a reference, and also it will hopefully help someone else.