older deployment target seems like a no-go

All of a sudden, using the AIR 17 SDK and Flash CS5.5, I can't seem to publish an ipa for my older iPad which is running, deliberately, iOS 4.3.5.  If I up the   <key>MinimumOSVersion</key>  to <string>6.0</string> then there's no problem on iPads running 6 through 8.3. Not sure about 5.0. First it worked, then it didn't. The error that I get on attempting to publish is one I've never seen before. Here it is:

There are no ANEs employed in this project.

I'm running from fairly unremarkable timeline code for this test. Even simpler no-code test-ipas are failing in the same way.

Is this a problem built-into newer AIR sdks? Or something else?