When opening a Visual Studio solution recently I was presented with a message box saying that “The project location is not trusted”.

Having never seen this one before I googled and turned up lots of posts related to loading solutions from UNC paths, which wasn’t the case here. The solution had originally come from a .ZIP file I’d downloaded and this steered the investigation onto a different track.

My environment is Windows Server 2008 R2, which it turns out has the facility to note and track files (of certain types I guess) which didn’t originate from this machine, checking the properties of the original .ZIP file shows a new button to Unblock the content;

Simply unblocking the file now won’t work, you have to delete the extracted files, unblock the .ZIP file and then re-extract them. Having done this, my problem was solved and I could now load the solution in Visual Studio.