Hey y'all

I just got a new IMac this week. It keeps losing the internet connection. I have an IBook too which I am on now which seems to have no problem and the IMac was losing the connection even when the IBook was asleep. The connection just disappears and then it won't let me rejoin the network.

Network diagnostics didn't help. Said maybe I put in the wrong password or something but I didn't. This computer has been connected to the internet for most of the last couple of days but right now it is out and it won't reconnect.
Any suggestions are appreciated, thanks.