I downgraded to HTTrack 3.42-3 and the 416 problem disappeared.  Before I did
that, I also downgraded to a copy of 3.43 and and the bug still exists there
too.  So this is likely a bug or regression that was introduced in version
3.43.

Looks like I will be stuck at version 3.42-3 for a while :|

Thanks,
Brian