The modem is connected through USB.
Groan. If I ever find the person who decided to run network communications over a technology as flaky and finicky as USB, I'm going to strangle them with a CAT5 cable...
Given what you've tried so far, my guess is that there's information related to the modem (or USB?) somewhere in Registry which has gotten corrupted or otherwise disassociated, and is now preventing the modem from being properly enumerated. If that's the case, even totally uninstalling and reinstalling the modem and driver may not help, as that process often doesn't clean up/correct such "loose ends".
I have seen instructions on different device manufacturer's support sites which tell you what Registry entries need to be fixed to solve "Windows cannot load the drivers" errors, but those instructions are all specific to the problem device. Unfortunately, I've seen no such instructions which apply specificallly to Surfboard modems.
You might try:
1. Uninstal the modem and drivers again.
2. Open the Registry Editor and look at the sub-keys under the following Reg key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB
If you find any subkeys related to the modem, delete them.
Make a backup of the Registry before you do so!!
3. Reboot, and reinstall the driver.