Can't access internet from my laptop!

[#1]

I called PLUSNET this morning and the guy told me he's going to e-mail me because it might have something to do with the brandband channel or something but I never got any e-mail.
Basically, My sister and mum can both access internet from their computers and my sister is using a laptop. I can connect to the router but can't open any web pages.  This is so weird, I used to be able few months but not anymore.
Any idea why that is?

[#2]

I suggest you temporarily try using a network cable to connect your laptop to your router.  If you can connect to the internet using the cable then you know you have a wireless problem.  If you still cannot connect then it's likely to be a fault on your computer.