This article may interest you, if after an upgrade to Dynamics CRM 2011, you open forms of certain entities and the form opens with an error message:
There was an error with this field’s customized event.
Error: ‘crmForm.all.tab2Tab.style’ is null or not an object.
You will encounter this error, if you use unsupported JScript customizations in Microsoft Dynamics CRM 4.0 that break the form loads in Microsoft Dynamics CRM 2011. Unsupported JScript methods include hiding controls, tabs, or menu items.
To resolve this issue;
1. Download the Microsoft Dynamics CRM 2011 SDK. The SDK has a list of new capabilities that replace unsupported methods
2. Then remove these kinds of customizations and instead use supported methods.
Note: SDK topic “Upgrade Scripts to Microsoft CRM 2011” contains information about how to replace the old, unsupported methods with the new, supported methods.