iPad and iPhone can't connect to my wifi network

10/1/13 - Last week updrade my software on my Imac and set up ICloud - could be unrelated to my problem.

1. My iMac and Apple are connect to my Belkin wifi system okay.

2. My two iphones and Ipad cant access my wifi - 'Unable to join network message'

I have search the discussion forums and tried most solutions - still can't get them to join.

Thanks

Kerry