We have several servers running 4.2.1 (Linux+Apache), when we noticed one project started to behave strangly after the upgrade from 4.0.6 to 4.2.1.
First we tough okay, a bug in the project -> nada, exact version is working on a 4.0.6 system!
So there must have been changes between 4.0.6 and 4.2.1.
The most important one, I think is the "register_globals" is now per default off.
So I updated our php.ini and now it is register_globals = On
(BTW: what is correct: On, on, 1 ??)
But still no complete success.
Is there anything else somebody should check when upgrading? (Any setting, any behaviour anything...)