Yes I do use a powered hub, and cable length is only about 3m from scope to computer. Mind you the hub is an older one, so not 100% it's working properly, might only be a USB 1.0 hub too... Will be upgrading once the bank balance recovers a little from my recent purchase

edit: this is the hub... looks like a USB 1.1
http://www.swann.com/webfiles/downlo...ezh_ezyhub.pdf
I never had a problem with the 400D doing it this way.