I successfully installed VZAccess, and after it finished, whenever I would plug in the USB551L I would get the blue screen of death...on Windows 7 (x64). I repeatedly tried uninstalling and reinstalling...all with similar results. Even if I didn't get the blue screen of death, the device driver installation would fail saying that it was unable to start the device. Then I noticed that the USB symbol beside the port looked a little different than the normal USB symbol. It had an "SS" prefixing it. After looking at the manual for my HP Elitebook 8540w, I found out that these were "3.0 SuperSpeed USB" ports. I plugged the USB551L into one of the regular USB2 ports, and it came up and started working fine.
So this device may not be compatible with USB3, or it may be that HP's "SuperSpeed 3" drivers are troublesome...either way I figured I would post here so that if anyone else has this problem it might help them.
I have a Lenovo W510 laptop and had the same issue. I thought it might be a Windows 7 X64 issues with the USB 551L Drivers. I spent days uninstalling and reformating my computer. I talked to Verizon Support about the issue and was told to contact Microsoft. The issue is the USB551L is not compatible with the USB3 Drivers that Lenovo has provided.