Several people encountered issues upgrading to MT4.2 Pro where they had been using "custom fields" (wonderful concept by the way).
6Apart have released a minor patch that should rectify the problem and are promising a minor point release soon to address this specific issue.
You can download the patch from here
To apply the patch follow these instructions:
* Download MT 4.2
* Download Upgrade.pm from the URL above
* Copy the downloaded Upgrade.pm over the file of the same name in your
download package.
6Apart have released a minor patch that should rectify the problem and are promising a minor point release soon to address this specific issue.
You can download the patch from here
To apply the patch follow these instructions:
* Download MT 4.2
* Download Upgrade.pm from the URL above
* Copy the downloaded Upgrade.pm over the file of the same name in your
download package.

