If I am reading your post correctly, I assume that you upgraded the pc5750 to the um175? Did you change the "Allow other network users to connection through this computer's internet connection" for the dialup connectoid that VZAccess manager created for the um175? If not, then your PC may still be trying to share the connection of the old data card, which is not being used anymore.
Go into the Properties of the dialup icon (in Control Panels> Network Connections) and verify in the General tab that it is on the correct device (the modem should show um175). Then change to the Advance tab and "point" the dialer to which LAN port it should route to.
I keep getting "username and password isn't correct for the domain" error messages....
Here's the issue (related to this UM175 device)
We have 2 computers, 2 usb modems and one mobile broadband account. A wireless router won't work for us because the one computer goes VERY mobile (out of range).
The mobile computer (and this one I am using) works using the MiFi2200 modem just fine (I am connected right now).
BUT, we want to put the UM175 modem on this computer.
The software for it is older than that used by the MiFi device. I managed to install the older software by removing the newer version and the MiFi is still working via my Windows Wireless control panel.
But I cannot get the VZAccess software to connect using the UM175. I've used the test WWAN device and it sees it just fine. But when I try to connect, I get errors: "Access was denied because the username and/or password was invalid on the domain" OR "the remote computer did not respond" OR if I look in the log, I see errors #678, 3008, or 691 in cases of unsuccessful connection. It does seem to connect and try to authenticate.
Is the old software the issue? Or, can you not use different devices? The username and password isn't prompted for though I did find a place where it says to enter said info. It also wants other information I am not sure of. The software is v6.10.10 (2247b). When I press check for updates via the wizard, it says it is the most recent version, but I know that the version with MiFi2200 is newer (v7x, I don't have that on here anymore so I cannot say specifically like with this version).