wireless connection between powerbook an


I have an iMac Power Pc G4 which is airport equipped and a powerbook also airport equipped. I am unable to get my laptop to connect to the imac which is internet connected via a cable modem via the airport route. I have turned on internet sharing in the imac and created a network on the imac.
Despite the airport being on on the laptop and entering the name of the network i want to join, I cant connect. The two previously had been able to connect but I had to get a new harddrive on the imac recently. No other changes to either system. The two computers are less than 20 feet apart at any time. I am at wits end, I have followed the instructions from the apple support site and the manuel supplied by the computers. Any help would be greatly appreciated.

Thank you.