Maybe. I've heard some guys have tried a hub, or usb splitter and it doesn't work having 2 things hooked up to the usb port on the back. I have a cheap usb splitter I paid $9 for at walmart (Targus brand) and have my EHD and Sling Adapter hooked together into it, and it works great. You can try a usb hub, and if it doesn't work, you'll have to plug one of items into the front usb port and have the front door open, which kinda sucks...
I would imagine that this might be true if a USB hub acts like a Ethernet "Switch" and not a "Hub". Hub where all connections are interactive all at once. A Switch where one device connects only to another leaving others locked out. Or two others while the two are. So two and two - 4. Not three. Which is what would be needed here.