shared house has shared router - but one computer gets bannished!?

[stephenn]

hello,
we have belkin router in shared student house. it has WEP security and is dynamic IP..........
every now and again one person with their laptop is unable to log on... it says that WEP log in name is incorrect and told to see admin.... this happens whilst we are all still connected and can see that the login has not been changed....

Q
if some mischeif person has access to admin (we actually all have).... can that person isolate one computer to 'not work' on our router?... the only thing we see in admin is MAC address control.... but this is still disabled so doesnt look like the method....
Any thoughts how... or how to stop?

the router is wireless and one person has a 'mains plug system' so they get the internet (still plugged into our belkin router) up their mains and have a plug from there to their computer.... are they the 'mischeif ones!!?? .... have we been hacked!?

any thoughts would help
thanks
Stephenn