Rather than asking for help on this, I'm posting a workaround I found.
While the MiFi 200 works fine via USB on a different PC and works fine via WiFi, VZAccess Manager was having great difficulty communicating with the MiFi 2200 via USB on my Dell laptop running Vista. I tried uninstalling and reinstalling VZAccess Manager, all Novatel devices in Device Manager and the Novatel device drivers, all to no avail. The symptom remained the same: sketchy communication between VZAM and the MiFi. Clicking Help->AboutVZAccess Manager always failed to produce any hardware info.
While poking around in Device Manager, I decided to try disabling the Novatel Mass Storage USB Device since I had already installed VZAM and the drivers. Bingo! Everything else started working normally. Of course the simulated CDROM drive that the MiFi provides for installing the software and drivers is now missing.
Perhaps this post will help someone else who encounters this problem. I don't know why this workaround allows the MiFi work on my Dell laptop, but it seems to be sufficient. If someone passes info on to Novatel, maybe they can come up with a real fix, or at least identify the cause.