There is nothing wrong with the server, nor has it been (to my knowledge) the last month. So the problem is very likely on your system. I suggest the following:
Remove avast, reboot and reinstall. See if it updates.
If not:
1)run a online virus scan
2)run spy-/adware removers
3)check your hosts file(s)
4)check your firewall settings
If that doesn't solve it, let us know here. In the mean time you can as alternative manually download the update(s) from
www.avast.com