Things I've tried:
-Moving to C:\Annihilus (previously just in an Anni folder on my desktop, worked perfectly). Doing this let me at least be able to open d2, but it's with the vanilla patch, and I get the 00005 error if I try to log on.
-DEP exceptions
-Resetting computer
-Fresh full install
-Cutting myself
Now I just get this error when I try to update. Everything is running as admin, so I just don't get it.