Has anything changed today maybe? There was a bug fixed in one of the scanning modules...
As for the name of the scanned file - the one you see in the program UI is probably not the one you're looking for, but rather the previously scanned one, or even a few files back (the display isn't updated for every scanned file, that would slow things down).
I'd suggest to start with the initial guess (the folder you see) - and then try to scan particular subfolders (or the following folder) using the avast! shell context menu - until you find the "bad" file (if you do, please don't delete it - it would certainly be useful to have it to fix the problem).