This could work.......
You could put a stair case that loops round and up where the back little room is. I know you're loosing a room but you will have the exact space downstairs and upstairs.
Okay - Its will sound stupid but try restating your router?
Try disabling your firewall on you're anti-virus software (If you have one)
I know you said you've updated you're drivers but have you rebooted you're computer?