i have a little minor problem with my N900.
It wont connect in mass storage mode when conected to my USB Hub. Hub is USB 2.0 and i never had any problems with any device conected to any port of it. I tried different ports.
On the front ports of my PC the N900 works without any problem.
(almost without any problems, the headphone connector is next to the USB Ports and if the N900 is connected there my Headphones get a bit "jammed".)