Network connectivity problems.
I have recently had to reset my router. Following this my imac (mountain lion 10.8.3) wont remember my network. I have no problem connecting to the internet but have to do it manually each time I reboot. There is now no option to automatically connect when selecting the network. Funnily enough if I remove the security password to my router the imac then allows me to automatically connect to my network. I have tried deleting Key chain and also my network settings with no joy. Please help.
iMac (21.5-inch Mid 2011), OS X Mountain Lion (10.8.3)