ice sounds like u got a 11mbit usb adapter.. 802.11b, as apossed to the 'newer' standard 802.11g(54mbit). From what i understand b networks will reach further then g for pure line of sight.. but will suffer from degradation alot worse as it passes through solid objects. better off getting an 802.11g pci card for each desktop.. will set u back around $30 something each so not that bad.
el
