Hello, I have the same problem, I used the Dell Mobile Broadband utility, and run the self diagnostic, and the result was  Failed:HardwareTest. I supose the device is not installed, or not connected to the Motherboard. How can I activate this device? there must be some configuration to do in the BIOS, or something is not pluged correctly for this notebook. mine is Latitude E6410, too, with Win7. I didn't see any reply for this post. please, the USB Modem is very annoying. Best Regards, Juan Carlos 
Hello Could you please help me I have a E6410, install sim card, load and start Mobile Broadband Manager and it say me an error "Mobile Broadband Device not found" I allready  download and install Wirless Mobile Broadband Drivers, both of them (5620 and 5540 mini card) i realy dont understand how to determine which of them installed in my laptop. Is there any clue ? Thank you in advance p.s. sorry for my English
Latitude E6410 Mobile Broadband Device not found