First question is: Do you own any MAC products, such as airport or express or whatever "i" there is.
if the answer is yes; then that is where you problem is. the mac wifi defaults to channel 6 (in router terms) an it competes with the BeoLine channel that happens to be along the same freuqency. This has started to occur about 5 months ago with the firmware update that mac always does.
To fix the issue. Open a phone line (call your cell) and stay on it. Go to your express i-thing and unplug it from the wall, wait 30 seconds plug it back in. It will look at the channel that it defaults too and once it sees it's occupied (because you are on the phone) it will jump to a different channel and your problem will be fixed.
Willie
B&O Store Calgary