Wireless range doesn't work past 5-7 foot

Incase my setup is bad.
My Dell TV is mounted on the wall (five feet up) and two feet below that is a table top my computer is on. On top of the computer is the cable modem that connects to a wireless router (I have that for a wireless xbox adapter in the next room). Maybe there is some interference from that because living room table it no more than six feet away from the keyboard/ mouse receiver and I can't move any further away, sit back on my couch with it, without the keyboard losing connection. I've changed batteries and moved from further away to up close and back and it clearly has a 5-7 foot range. Probably get for a desktop but I've a 42" monitor.

Wireless Keyboard and mouse

Over all this is a great set up. I just wish these devices were rechargeable. That being said i havent had to change the batteries after a month of use (i use this device in my office so they are being used from 8 to 5). One great feature is that it will operate a few feet from the reciever, not like the microsoft keyboard mouse combo i used to have. There are plenty of controls on the keyboard and extra buttons on the mouse as well. I have been very happy with this keyboard mouse combo!