Are you using a "N" router to connect to the dongle and if so make sure you are following the manual recommendation that the security, if used, must be AES encryption otherwise the transmission rate will be limited to 11g (54mbps).
SEE page 23 of the manual for the commended modes and the important comment that for Peer to Peer mode the max transmission rate is also 11b/g.
I am getting very good transmission through a couple of brick walls that means it is actually faster to send over the wireless network than saving on a USB hardrive and then reconnecting and downloading to my computer. My playing of ts files is absolutely sooth .
BTW I am using a recently replaced box with v1.75 firmware and the unit is working very well.