Sometimes, when you try to add BTAHL7 Common Project to your solution you may encounter with the error “Object Reference not set to an instance of an Object”.
I am not sure how to resolve this error, but there is a simple alternative to this Error.
This error will fail to add the necessary common schemas (for eg: datatypes_25.xsd, segments_25.xsd, tablevalues_25.xsd) to your solution.
All of these schemas would generally be available in the following path. <drive>:\Program Files\Microsoft BizTalk 2010 Accelerator for HL7\Templates\Schemas\V2.X\
So, you can Create a new Empty BizTalk Project, Copy these common schemas to your project folder and Add them to the Project using Add Existing Item.
Please post if you have a solution to resolve this.