C# Outlook 2010 AddIn Form Region and Registry Entries

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C#

.NET

VSTO

Outlook

.NET4

AddIn

Hi all,
I have an Outlook AddIn, which has custom form regions with message class name IPM.Note.XXX (for MailItem related Form Regions) as well as IPM.Appointment.XXX (for AppointmentItem related Form Regions), where XXX varies for different form regions. In a particular issue however, it is observed that, on the double click of date in a calendar or on click of a "New Appointment" menu option in the ribbon, my custom form region with IPM.Appointment.XXX is invoked. This is not the intended behavior and no code has been written for such thing to happen. Also, I have checked the registry entries, and those seem to be fine.
I need to know, what might be causing this issue?
Where are the entries for default outlook FormRegions made in the Registry and can such standard outlook information may have been over ridden?
Also, it is observed that on a particular machine, one of the default menu New options' text in the Main Ribbon's Home tab with Calendar selected in the explorer, has changed and I am not able to understand, how is it possible...any thoughts on that?
Also, is there a possibility of interference from any other AddIn and if so, how to find it out?

Thanks, Bhushan.