InfoPath Dev

We have InfoPath 2003 and SharePoint 2010. In SP2003, I would just normally add a link to my outlook message such as this: http://..../..../infopathform.xml and it will open the form in Edit Mode.

However, after we upgraded to SharePoint 2010, the same hyperlink will only open in Read-Only Mode.   Is there an easy way to fix this problem without going through regedit?

Much appreciated. 

 Do you have check-in and check-out turned on for the document library where the infopath form goes to? If so, I think this might be causing Sharepoint to provide the form to the user as Read Only. They need to 'check-out' first.