Are you using the free version? Something very strange going on here. I'm still on 315 release date 8.9.03 it was just the program version that has updated but with the release date 26.02.2003!!!! Just tried to update again and it said I was up to date.
I'm confused too. A couple of days ago someone posted in a thread that 516 was available. Later the same day I tried updates and all I got was 515. A few minutes ago I got 516, and yet some people are already downloading 518.
With the program update of September 8, AVG 6.0 now supports smaller update files! AVG 6.0 customers will benefit because of the quicker distribution and download times of the new updates. In order to take advantage of the smaller update files, your system must be on version AVG 6.0.516 or higher.