Airport help please..

Ok guys if any one can give me a quick fix on this it would be great.

I've had my mac for 6 months, I have had no problem connecting to my wireless connection until today. Now I have just picked up my imac this morning from the mac store as they had to replace my logic board because of a faulty firewire issue but now I cannot connect to the internet. My laptop connects fine (I'm on that now so it isnt my network) but my mac aint connecting. Airport can see my wireless network with a full signal and the other networks in the area but when I try connect the airport symbol in the top right just switches to an ! mark.

Now I obviosuly reckon they guys in the mac store screwed it up but they are close till monday so.... any thoughts guy? Is the airport reciever connect to the logic board? Is there a way I can re-configure?

Brian

I would re-check all your settings and password as you said it can see your network and
shows full signal and try join network and see if it prompts you for a password.