A: It is possible that the Compact Flash Memory Card inside the instrument has come loose.  Open up the connector endcap and pull out the battery (it is not necessary to remove the battery).  Look inside the instrument, and you will see a faceplate with a cut-out for the memory card:

Push on the memory card to make sure that it is fully seated in the memory card holder, then try offloading data again.  Take care not to push on the card ejector button when you are pushing the memory card back in place.