I've done some research on this subject and found the following:
1. Everyone will find different content in these files. (It appears the files contain data from another file on your PC.)
2. The temp files have a date and time that coincides EXACTLY with when a scheduled AVG test COMPLETES. See the picture at the URL below for an example of three sets of temp files and three AVG tests:
I hope Grisoft will now take this issue seriously.
My theory is that AVG has problems with locked files. Here's why I say this: When I've looked at the one large temp file that has any data in it, the file appears to be a copy of another file which I KNOW is locked.
So, it appears that AVG is having problems with files which are locked by other processes.
I noticed this problem starting about a week ago. I noticed it because one of the temp files that is left over fills up the disk where I have the TEMP directory, so it affects my other programs.
I'm going to post this same message to the Grisoft forums, hoping they will look into this (now there there is some pretty concrete evidence.)