A very long known false positive. There is even a sticky about it: False positives in au3 extensions
The question is not why did it raise alarm but why did not it raise alarm before?
The Extension Manager is coded with tools (AFAIK Auto It) that can be used for bad things also.
Anti Virus Softwares do not like these compiled Auto IT codes.
Make sure that nothing has been changed by a new threat - that is all.
Re-install or just compare a copy of the Extension Manager from a known good source.
If the alarm is the same & the sizes of the files - it is ok.
p.s. Maybe keep a spare to compare at Your PC in the future.
Edited 3 time(s). Last edit at 06/23/2013 06:10PM by guenter.