I was having the same problem, but then I realized the program was connecting to your server and finding a newer available version, so it couldn't be offline. I had an old copy of the EXE with the 60ish camera mods I'd made that I tried to use.
Anyway, long story short. Avast anti-virus was blocking access to your domain because "Blacklist:URL". I have no idea why and it certainly isn't in any blacklist that I made. Just FYI, you probably can't do anything about it.