avast! 5's Behaviour Shield blocked upgrade of Privatefirewall. I had to stop avast! 5's Behaviour Shield before I could upgrade to the newest version of Privatefirewall.
System Anomaly Detection was already off. I'm not using it on XP.
avast! 5's Behaviour Shield doesn't work in Win 7 64bit so I use System Anomaly Detection for Win 7 64bit.
Sound confusing? Privatefirewall's Behaviour Shield is known as System Anomaly Detection.
Due to avast! 5's Behaviour Shield doesn't work in Win 7 64bit, I didn't have any problem upgrading Privatefirewall in Win 7 64bit.