We came across this really tricky situation and we would like to thank Microsoft for having a KB article (http://support.microsoft.com/kb/949941) for this.
We wanted to bulk edit a few of the accounts using the Actions => Edit option. The form that comes up here displays all attributes available for the Account entity. You would however notice that some of them are disabled though. Since we had 2 custom picklist type of attributes, one showing up as enabled the other disabled, it was easy to identify the possible reasons for disabling this one had custom code written on its onchange event while the other did not.
But we still wanted to be able to Bulk Edit this attribute without having the need to create a custom page just for editing a custom picklist attribute. Our search lead to the following KB article that explains the steps to enable this.
To have this explained in short, the entity customization file has a property “BehaviourInBulkEditForm” for the event tags. This determines the behavior of the attribute and the code written on the event. The valid values are
Enabled — If you use this value, the field is enabled. Additionally, the code for the event is run when the event is called.
Disabled — If you use this value, the field is disabled.
EnabledButNoRender — If you use this value, the field is enabled. However, the code for the event is not run when the event is called.
Exporting the customization and making the below change should enable the attribute and not have the code written on the onchange event fired