The situation is exactly the same in both cases.
I must say I don't know what to think about it... either there's a problem somewhere in avast! engine - but I'm not aware of any recent changes to the related pieces of code, or... there's a rootkit/malware spreading, manifesting with these symptoms.
Well, I'm sure there are other explanations, but these two look the most likely to me at the moment.
Can you find (e.g. in the scan logs) what was the first time this was reported (which, in your case, probably means when you installed avast!)? I'm looking for the first version of the virus database (if there was a new problem there, it would be easier to find knowing when the change happened).