Well, a few shots at this.

  1. You have Win32:Vitro/Sality. Long shot, but possible.
  2. A VPS Update or Engine Update accidentaly marked it as suspicious. Furthermore, if you ever find a program with a 100% Detection rate (atest threats) with NO FP’s what’s so ever, let me know :-). PS: You won’t ever.

http://imgur.com/r/howto/gobnA4G