Mobile internet USB device problem

I am having a most irritating time with my Vodaphone USB mobile internet device. It will work happily for days then suddenly I get the dread message, No Device. A combination of reintalling the USB 2.0 driver from disc, repeatedly rebooting and physically taking the device out and plugging it back in gets it going again eventually, but I know it's only a matter of time... Also Windows often informs me it doesn't recognize one or another USB port - later it does of course - and often tells me the device would run more quickly if I plugged it into a USB 2.0 port. Thing is, all the ports are 2.0!

Anyone please tell me what's going on and how I can fix it?

Many thanks