problem with macbook connecting to wireless: help please

thanks for reading this thread.

i have a linksys WRT54G2 router connected straight from the ethernet port of a cable internet connection. it's been working fine for the past month or two for both me (using macbook 10.5.6), my flatmate (running vista pc) and my girlfriend also running a macbook.

but, the last few days i've been having problems getting connected. which are:

not connecting to wireless network automatically, and asking for password which is already remembered in keychain
getting connection timeout when trying to connect
getting invalid password, even though password is correct
websites taking around 2 mins to load when connection is eventually made

the internet is working fine on both my flatmates and girlfriends computers, but jut doesn't seem to like mine. heres what i've done already:

restored router to factory settings and updated with latest firmware
cleared all known wireless networks within network preferences
tried both firefox and safari
accessed router using IP address and loaded pages instantly
works fine connected to router with an ethernet cable

the only thing i havn't tried is a different wireless network, which i'm going to try tomorrow when i go into university.

has anyone any idea what the problem may be? like i said, its been working fine for the past 2 months but has just decided it doesn't like my macbook.

any help or suggestions would be great, thanks alot

 

the funny thing is it's working now, but now it's not working with my girlfriends.

i'm using a WEP key and my girlfriends macbook says incompatible security. hers is a 2.1Ghz macbook running 10.5.5 and mines a 2.2Ghz macbook running 10.5.6. any ideas to that?

 

i used a different name when setting up a new network.

does anyone know how to set up WPA2? when i go to the linksys setup page in the browser and go to wireless security then choose WPA2 it doesn't generate a passphrase for me. i'm not sure if it requires just hex, ascii or just anything.

also, i tried a different wireless and it worked fine. it's now also working fine, but occasionally getting connection timeouts and slow pages, but probably something i can live with.