I have been having this problem and getting this error trying to update AVG Anti-Virus 8.
Invalid Update Control CTF File
To fix this:
1. Navigate to:
For WinXP: C:\Documents and Settings\All Users\Application Data\Avg8\update\download
For Vista: C:\ProgramData\avg8\update\download
2. Delete avginfoavi.ctf and avginfowin.ctf
I did this a couple of times and the error just kept coming back the next day. So I took the next step of downloading and installing a fresh copy of AVG 8 after removing the original program. Guess what? After spending a grueling 6 hours downloading and installing the new AVG, I started getting the same error. So, I am back to square one and back to deleting the files again.
I have done many searches on Google and find these same fixes time after time. It seems to fix the problem for most people but I guess I am not most people.
**Update** After a few weeks this problem finally went away on it's own with no extra help from me or anyone else. So, if you are still having this come back time after time, there is hope, just keep on deleting.
**ANOTHER UPDATE** Here it is nearly two months later and after thinking that this problem was solved, I got the same error again today on Dec. 17, 2008. Please, if anyone knows of a permanent fix for this besides ditching AVG altogether, post your solution in a comment below.