Related Activities in CRM Online

I've created a C# app that bulk loads activities and assigns them to an Account. This works successfully on CRM 2011 on premise, and appears to work on CRM 2011 Online.

However, when using the new Account form in CRM 2011 online I cannot see the activities, only when using the 'old format' form.

Are there any changes I need to make to get the new forms to appear correctly ?

Thanks