Hello Darwin,
I understand that you are unable to update AVG and get error "Out of date". This is caused due to the synchronization error with AVG update server. Please remove AVG Internet Security from your computer control panel and install latest version of AVG from this link http://support.avg.com/SupportArticleView?urlname=Download-and-install-AVG-AntiVirus-Internet-Security-or-Premium-Security.
If you face any difficulties, please let us know and we will assist you further.
I had this problem. After spending hours uninstalling trying to reinstall, this finally fixed it for me.
On my Windows 10 PC, my DNS servers are set to my router address (default gateway). I changed my DNS to use google DNS servers (8.8.8.8 / 8.8.4.4) and then the update worked. I also looked at my ISP router and saw what DNS they were using and used those addresses and it worked too. So it's something with the router forwarding DNS requests. But if you change the client to use DNS Servers, AVG defs update.
Hope this helps.
Hello Darwin,
I understand that you are unable to update AVG and get error "Out of date". This is caused due to the synchronization error with AVG update server. Please remove AVG Internet Security from your computer control panel and install latest version of AVG from this link http://support.avg.com/SupportArticleView?urlname=Download-and-install-AVG-AntiVirus-Internet-Security-or-Premium-Security.
If you face any difficulties, please let us know and we will assist you further.
Wound,
Thank you for sharing the valuable information here. We appreciate your efforts in trying to resolve the issue. Yes, it will help most of the customer who are facing this issue. Please feel free to contact us if you have any further questions.
When starting AVG internet security, message is definitions out of date…UPDATE
Try to update but get error message "unknown error", that makes 2 of us 
The file it trying to download is servers.def.vpx
Anyone got a fix.
Thanks for the help
Darwin