C640 True Mobile 1150 mini will work on some but can't see others

My c640 wireless works on some networks but can not even see others. It is not loaded with the original software but does have XP Pro. It currently will connect to The Comfort Inn network where I am staying but it can't see my home or my office's network and could not see the network at another Hotel. I installed the utiliy, and driver for the mini from Dell Support but no change. My wireless network connection seem's to see my home wireless when it is booting up but if I try to connect to it the connection says there are ne networks in range. Would be thankful for any help with this.