Thanks for the update Lukas.
I'm running my own test with rapport - so far inconclusive. A problem with tests is that the firewall stops are infrequent and irregular - sometimes it runs fine for a few days (when I say a few days - I should point out that my machine is only turned on for a few hours each day).
I uninstalled rapport, rebooted, and everything with the firewall seemed fine. Then I re-installed rapport, and after a few hours the firewall stopped.
I uninstalled rapport again and rebooted, and fairly soon ater the firewall stopped again!
I rebooted again and everything has been fine since (for over 2 days now).
So I don't know if the reappearance of the firewall problem after rapport was uninstalled (+1 reboot) proves that rapport is not the culprit?
Alternatively, can a second reboot after rapport uninstall achieve something that the first one didn't, meaning that rapport may have been responsible after all? (but not that it definitely was)?
Beyond me!
In another couple of days if everything is still OK I will reinstall rapport.