It turned out I was right, it's because of Avast... (I guess some other antivirus could do the same but there's no way I can test them all :/ )
I don't use it myself (and I would also recommend that you don't) but the culprit is this :
it completely screws up the detection.
I would recommend that you add Updater.exe to the exception list (make sure to add the program, not the shortcut).
Thanks, I'll check it out when I get home. I have AVG, which I guess is owned by Avast now, so that's probably it.