Ragnor: How many wireless networks are detected in your area?
Could you temporarily try his wireless adaptor in your machine? You might be able to narrow it down to a problem with your current adapter. If you find it's your adapter you could just get a newer one.
Other than that I can't think of anything that's not difficult or expensive. Figure out a way to run an ethernet cable, look at ethernet over power options like the Netcomm HomePlug NP285.