One question, if I may - avast! 4.8 (not 4.7 though) checks Windows catalogs to see if the particular file is a genuine system file. If it is, the false detection doesn't occur. On the affected computers, this check has obviously failed...
So, anybody affected by the false alarm with avast! 4.8 - have you installed any tweaking tool that may have deleted the catalogs (I was told nLite / vLike might possibly do that - though I don't know them myself), causing the file not to be recognized as a Windows system file?