This combination of hardware and service works just fine.
In the Cradle point web based administration tool, usually accessible from 192.168.0.1 go to Basic > WAN > Cellular Modem PPP Authentication (optional) and select ExpressCard then enter the information provided by Mobi for your username and password. Choose "Auto" for Authentication Protocol.
Then go to Modem > Settings > Modem Specific Settings > Access Point Name (APN) put in:
mobipcs.com
That should do it; contact me if you have any problems.