InfoPath Dev

I am stuck with this problem when i preview an infopath form:

The query cannot be run for the following DataObject: GetCommonManager

InfoPath cannot run the specified query.

The SOAP response indicates that an error occurred on the server:

Server was unable to process request. ---> Object reference not set to an instance of an object.

does anyone knows what can I do to solve it?

I searched EVERYWHERE, logs and forums, and can't find a solution.

It happens only on GetCommonManager. for GetUserProfileByName, it's fine. 

Any ideas?

Allrighty. i found the answer. although it's weird.

The managers name of the user was blank.

Although i can swear that even it was blank before, it didn't give me an error.

Solved :)