Messed up internet connection on laptop - help?!?

[jammy]

Out of the blue, my laptop doesn't have a proper internet connection, and when I open Internet Explorer, instead of it saying the usual 'It cannot find this page' it just stays as a white screen and freezes.

My laptop says it is connected to the wireless connection but it's clearly not. I've tried switching between wireless networks but it does the same thing to every one and it's been like this for a week now. Is there a switch on the laptop, have I accidentally done something or is something wrong internally?

Thanks.