MBP 10.5.8 won't see wifi network but iphone & ipad ok

not only that, but the pc's in the house runing xp, vist and 7 all see the network. i have access to the modem but am really reluctant to change anything for fear of disturbing everyone else's access. i've never encountered this with my macbook pro before - i've always seen networks. i can see many of the neighbours networks too. i have included a screenshot of the modem settings. i'd love some help! also, yes i am in Brazil and password is 10 characters [6 numbers and 4 letters]. Graham.