Did you ever resolve this? We have had the same issue with four different M275 tablets, all using this same Verizon card. I did find that Verizon just released a new version of their access manager software (v5.1.0). This update fixed the problem on one of our tablets, but not on the other 3. The software update can be found here:

http://vzw.smithmicro.com/download/

Hope this helps you!