This morning, AVG reported no error after an automatic update. But, when I checked the statistics, the last update is 12 Aug 08 and virus DB is 270.6.0/1602.
On checking AVG website, the latest virus DB is 270.6.1/1605. I did a manual update twice but it failed. I downloaded the file manually from AVG and the first update changed virus DB to 270.6.1/1602. The second update did not change 1602 to 1605 because the installation is corrupted. After downloading again, the same problem happened.