That is a very odd error report for a piece of hardware: are you using management software from Zyxel? If you are, try it without and see how it goes. Uninstall the entire thing (hardware and its associated software), reboot/cleanup, and then install only the hardware with its driver (just plug it in and point Windows' hardware installation dialogue to the driver's location if necessary. This is based on the simple rule of thumb that Windows' WZC (and the Vista equivalent, which was renamed) is usually better at W-LAN network management than the supplied utilities. Why they are still routinely provided when Windows 98/ME is but a distant memory for most folk, I don't know! Seems like a waste of development costs.
Another tip: make sure that any problematic devices have a minimum of things in between them and in plain sight, away from big thick solid things. Straight lines are better than diagonals, with less floors/walls to deal with, since this is just nothing more than a high frequency radio signal.