Can't connect through wireless

[#1]

Hello
Please help my plusnet broadband supply is up and running but i cant connect through the wireless facility although i could earlier, but with the ethernet cable its working fine, i don't understand why it would suddenly stop working??? Any help would be appreciated

[#2]

The reasons are manifold!
What model router are you using and what operating system are you using would be two important pieces of information.
Did you change anything at all between when it worked and when it didn't work?
Do you have a laptop?

[#3]

It's a thompson gateway supplied by plusnet and OS is XP, laptop can see the neighbours wireless but plusnet is not always there even tho i have all green lights lit up on router, at the moment its working but then it will disconnect and plusnet will not be visable????? not sure why

[#4]

Are your PC and router reasonably close?
When you do see a signal from Plusnet is it reasonably strong (and stronger than all your neighbours)?
If a laptop, does it help to move closer to the router?

[#5]

Changing the channel from 1 to 11 in the router setup pages worked a treat for me.