That error means there is a program running on port 15779 on localhost. Joymax added that check a year or two back to break all of the programs that faked out the client connection.
Here's a view of the check in the latest client (you'll need an unpacked client):
If you make that JNZ a JMP, it skips the error message. Otherwise, you'll need to free up port 15779 from whatever is using it.