Is the modem connected by USB to one of the netbook ports or the Hub? Try connecting it directly to the netbook, switch off your firewall temporarily and try again.
Your Hub is self powered and therein lies your problem. Each USB port on the computer can deliver only a certain amount of power and as soon as you put the hub in that is split 4 ways which obviously is only enough to support your mouse. You need to buy a powered hub.
I have a cheap self powered hub which I can use to support a wireless mouse transceiver and one laser printer. It won`t take a second printer or scanner at the same time although I can plug in a memory stick.
For a brief explanation scroll down to power at click here