ACZoom

The subject line is pretty cool - "gone mad" :-) Not possible really, just code behaving in a way we need to explain now!

Is the count really one? Check the actual count for the IP address in hosts.allow, in the second section - lines starting with #bh: ip:
If that count is at threshold, then the next attempt would block the IP.
The above logs seem to indicate that --blacklist option is not being used, so that may not be a factor here, but that is another way an IP would be immediately blocked.
Last resort is to retry the test, and rung with --debug option - lot of output, but it may provide a better clue.