Either you have connected to Team Foundation Server for the first time or changes have been made to the field mapping between ...

Either you have connected to Team Foundation Server for the first time or changes have been made to the field mapping between Team Foundation Server and Office Project since the project was last refreshed.  

Data in fields with a mapping status of 'New' will be replaced with values  from Team Foundation Server. You can still view data in fields with a mapping status of 'Removed', however, you cannot publish or refresh the data in these fields.

Click 'Cancel' to prevent data from being overwritten or deleted, and then copy the data in the newly mapped fields to unused fields in the project.