I had been tearing my hair out because my new HTC Desire couldn't see my home WiFi and yet occasionally it would "see" a weak signal from a neighbor's house. My Access point was running WEP so I changed it to WPA-SPK - still no good. So I also set up a second standalone WAP running WEP. Still couldn't see either WAP. Upgraded to latest ROM firmware. No difference. Long story short, it wasn't the type of security, it was because I was using Channel 13 It suddenly occured to me that not all countries (I'm in Australia) have Channel 13 available so the phone might not have it either. THAT WAS IT!! Changed WAP from 13 to Channel 6 (although any other but 13 would no doubt work) and everything worked.