Because I had forgotten the password to my WiFi router, I had to factory reset it. When I tried to enter the same password I had previously, it was rejected because it contained a space. Considering I entered this passphrase before and it worked, one can only assume some middle manager at Belkin decided it was ok to require passwords NOT to include spaces.
Funny, I no longer have space for Belkin (or Linksys) products in my life.