Issues in connecting wirelessly with Mac Powerbook and Linksys Router

OK. Here's the deal. I am entirely frustrated and also over my head trying to solve this on my own as I have no idea what I'm doing.

I have a Mac Powerbook, OS X (3.9). I have always connected to the internet wirelessly through my Linksys router (Wireless B Access Point, Model Wap 11).

I have recently moved and now use Comcast for my internet. When they installed my internet, I had not yet unpacked my wireless router, so I was set up to be connected via the actual cable plugged in. Now that the router is all set up, I cannot for the life of me get my wireless to work. Currently, I can use the internet wirelessly in other homes/school no problem. In those cases, I don't do anything, I just turn on my computer and it connects automatically. But for some reason in my apartment I cannot make it work.

I *think* the problem lies somewhere in the IP address area? If I look at my Airport settings and go to the TCP/IP tab, there is no information contained on the screen. Meaning, in the area where it says IP Address, Subnet Mask and Router, there is NO data listed, just gray empty space. The same goes for the DNS Servers and Search Domains areas, but at least in that case there is a white box to input text.

I can choose the "Configure IPv4 Using DHCP Manually" and that will let me input numbers, but I have no idea if I should even be playing around with this.

Also, perplexing me even more, is the fact that I can choose my Linksys internet connection through the Airport screen, and when I have selected it, I show full bars. But I can't actually connect.

Silly me, I attempted to call Comcast for help with the issue, but they say that as long as I can connect to the internet in any way (plugged in) then they do not care that I can't connect wirelessly.

I miss checking my email in bed...someone please help!!!

Thanks a million in advance for any and all help.

-kt