I bought this modem because the cheaper one that I had didn't seem to connect well. This one uses the same software (LSI)as the cheaper modem and connects using the USB2 port of my Dell Laptop (Windows 8) at a speed of 50k, which I'm happy with. It doesn't work on the USB3 port, returning the same error message as the cheaper modem. I'm following this up with US Robotics technical department, who seem very good. They return e-mails promptly and seem very helpful. Update: I've traced the problem to the Renesas USB 3.0 Host Controller. I uninstalled this program, downloaded it again from the Dell site and reinstalled it. The modem now seems to be working, so I've upgraded the stars to 5 - especially as the support from US Robotics is good.
Bought this modem for UK Caller ID, works perfectly after downloading drivers from www.usr.com/support/5639, set region as 'UK' in the device manager properties, and send command AT+VCID=1 using a serial comms application such as PUTTY.