The compass appears to use serial SPI communication. We have followed up on the similar post you put on our forum:
http://forums.labjack.com/index.php?showtopic=4918"
Sounds like you are talking about the LabJack U12. Sounds like your signal has too much impedance and can't properly drive the U12 analog inputs. See the following from our forum:
http://www.labjack.com/forums/index.php?showtopic=889"