I can't walk you through this with a click by click.
But I will share a STUMPER that I encountered a short time ago. The symptom was just like you presented.
What caused it?
The router was set to Europe and the channel was out at channel 13 since no other routers were found out there.
It was a real stumper.
I can connect to my wireless network (through my linksys router) fine through my own laptop, but when my friends come over with their laptops, they can't connect to my wireless (it doesn't even show up on their list of available networks), and I can't connect through my Kindle. I think I may have hidden my network somehow, but I am completely tech-deficient and terrified to start changing settings. Can someone help? (And walk me through any steps, seriously, I have a hole in my brain where most people's computer-speak is)