I'm using an Acer Aspire One A150, running Ubuntu Intrepid Ibex 8.10, madwifi-hal drivers as instructed here.
I was not able to see my wireless network even though it could detect and join other networks. The problem was caused by the wireless network being set to a radio channel higher than 11.
1) (recommended) Change the wireless AP channel to between 1 and 11.
2) If (1) is not possible for you, follow squire_uk's forum post made on February 10th, 2009, 06:11 PM for his fix.