The IDS MC must be updated to the corresponding release version on your sensor before importing/adding your sensor.
If your sensor is at version 4.1(4)S91 the IDS MC will first have to be updated itself with the IDS-K9-sp-4.1-4-S91.zip IDS MC update file.
If your sensor is at the latest signature update version 4.1(4)S130 then the IDS MC will first have to be updated itself with the IDS-sig-4.1-4-S130.zip IDS MC update file.
So determine your sensor version, then update the IDS MC with the corresponding update to match your sensor version. Then you should be able to import/add your sensor.
The IDS MC updates corresponding to the sensor versions are located here on CCO:
http://www.cisco.com/cgi-bin/tablebuild.pl/mgmt-ctr-ids
You will need to search through the links under:
IDS Sensor Updates -Version 4.X
If you are running an older sensor version you may need to access the "Archive" links in that section to find the corresponding IDS MC update file.