I have applied hotfixes to all DBTech mods that prevent those critical errors.
We are still not officially supporting vB 4.2.2 on PHP 5.4 due to lack of extensive testing. DBTech will be upgraded to a newer version of PHP later today.
Once we are confident our mods work correctly on PHP 5.4, we will begin official support for PHP 5.4 and vBulletin 4.2.2