Thanks for the feedback! I'm sorry for the error which I guess is related to the way I detect the directory from which the game is executed.
string workingDirectory = Directory.GetCurrentDirectory();
I did some research and apparently the correct way to do that would be:
string workingDirectory = System.Reflection.Assembly.GetEntryAssembly.Location;
I've never seen the old method cause any problems before even though I've used it on tons of computers.
I'll try to fix the problem as soon as possible.