I am in the process of testing an upgrade from a Zope 2.8.4 system to a Zope 2.9.1 system. The process I used: 1) Install 2.9.1 on a Win2003 system (it happens to be the same one that the 2.8.4 system is running but I changed the config so the ports don't conflict). The installation is successful 2) Copy the Product directory from my functioning 2.8.4 system instance to the 2.9.1 instance 3) copy the ZODB from the functioning 2.8.4 system to the 2.9.1 system All appears to go well -- the 2.9.1 system appears to be running everything from the 2.8.4 system correctly. A deeper check though shows that a few Python scripts in the ZODB (this in a system that has 20 or 30 scripts) fail. Examining the scripts indicates an error at line 3 -- but no such error can be found, however saving the script with no changes eliminates the error and also causes the script to now function. After finding and correcting these scripts everything seems to be working well. Any idea what happened during the upgrade to cause this strange behaviour and how can I avoid it? I will have to go through a similar upgrade at a customer's site and would like to avoid hand checking every script if I can avoid it.