Today I received the following error while trying to load a SOAP service reference in Visual Studio 2013.
Failed to add Service Reference 'Servicereference1.reference' Error: Unable to check out the current file. The file may be read-only or locked, or you may need to check the file out manually.
The message sounds like it's trying to do something with source control but I hadn't added the project to any source conrol nor did the UI indicate that it thought it. My default source control provider currently is "Microsoft Git Provider" and that seems to be where the bug is.
The solution to temporarly get my service reference added was to go to "Tools->Options->Source Control" and change the current provider from "Microsoft Git Provider" to "None", after that I was able to add my service reference. I also tested and I was able to add "Microsoft Git Provider" back after setting the service reference so this seems to be an Ok workaround. I tested this in both Visual Studio 2012 and 2013.