I haven't had any problems with Norton, and I've been using it for over 10 years. There's just nothing in the file to alert on. My guess is that AVAST may be making the generic assumption that an .exe file, especially one with a boatload of (compressed) attached data may contain a virus. If that's the case, it would be better to internally uncompress and scan it - but that would slow performance. Not sure how Norton manages it.
Proof in the pudding would be to have Avast scan all the extracted files - if it passes, than indeed it has not scanned the internal files (uncompressed).