I always get that "you're not fully protected" message when upgrading, but haven't seen the "general error" one with the 2014 version. Sometimes the server is busy or temporarily inaccessible and you can get a similar message, so I'd keep trying. One thing I'd try would be to download MalwareBytes (MBAM), get it up to date, then boot to Safe Mode and let it do a full scan to be sure you haven't picked up some kind of malware.
I just installed 2014 AVG AntiVirus Free on 9/22/13. The first alert I got was "You are not fully protected!". Under computer, it notify's me that the "Database is outdated". When I attempt to update, I get the pop-up in the lower right hand corner of my screen notifying me of a "General Error".
I am using a Dell Inspirion 1545 (4 years old). I have Windows Vista Home Premium (64-bit operating system).
Please let me know if you can support. Please let me know if you need more information from me to help resolve.