Can't find Airport Express Base Station on OS X 10.6

Hi there!
I am in a bit of a clinch regarding the set up of my new Airport Express, and am hoping someone will know a little about how to resolve my problem.

I have an older iMac 2,4GHz, and recently upgraded to OS X 10.6 as I need more memory before I can install 10.7. I also just changed from a D-Link router to a new Airport Express as there is also a MacBook in the house as well, and we wanted to have a shared online connectivity. We were going to use my Mac to set everything up, only to have issues with getting the Express going.
In the end we used the MacBook to set up the Base Station, and internet is working fine with both this, the iPhones and iPad. However, my iMac does not want to play.

Airport Utility can't seem to find the Express, even though I can see the wi-fi present in my network list. I have tried rebooting the Express, change and remove password, change between WEP, WPA, and WPA2 without it giving any positive results. The MacBook has allowed for Internet sharing, so that's also ruled out.

I found a post that said I should delete all previous Keychains, repair my HD in Disk Utility, reset PRAM and startup in Safe Mode to try and connect. No luck here either.

So now I am at a loss, as I don't know what else to do to be able to find the Express, and therefore connect to the internet?
If anyone out there has any suggestions, they will be very well received and much appreciated!

Is the iMac connected Wirelessly to the network?

To begin with I could at least select the network and attempt writing the password (unsuccessfully), and the response was just Connection failed, but now I can't even select the network any more.

dtravis7 said:

Is the iMac connected Wirelessly to the network?

Click to expand...

Airport Express problem resolved

So I kept at it and tested different settings, and I must have done something right, as it is now working!
In network's advanced menu I copied the exact same details that was stated in TCP/IP and DNS under the MacBook's details over to my iMac, and suddenly it was connecting automatically like it should. Not sure which of the two tabs did the trick for me, but I am happy I got it working.
Cheers for your response dtravis7!