I’ve been getting “Invalid Update Control CTF File” errors for quite some time whenever I try to update my local copy of AVG Free, the virus protection I use on my Windows boxes. I finally dug around and found the solution to the problem.
Some of the downloaded files are corrupt. (I actually assumed that from the error I received. Is nice to know I was correct.) You have to go into your Windows Explorer and delete the *.ctf temp files in C:\Documents and Settings\All Users\Application Data\Avg8\update\download\ Don’t delete the *.bin files as those are the ones that were compiled on previous updates. (It would be nice to see them all made into one file though.)
I hope this helps someone.
Update: I know I wrote this post for WinXP users but Doug notes in the comments below that Vista users can find AVG’s saved files in the C:\ProgramData\avg8\update\download subdirectory.