HELP!!!!
I'm having a similar issue with my 2009 iMac (MID) running 10.8.3. I am using a Linksys E2500 router.
On start or wake up I have to select my wifi network every time and enter the password. I check the box to remember the network but it never does. I keep getting the message that it cant find any preferred networks.
As long as the Mac stays on and doesnt restart or enter sleep mode it works just fine.
If the computer enters sleep mode it does not connect upon waking up. Again I have to select my network and enter password. I have to do this every time.
If I turn off wifi and turn it back on it does not solve the issue. I again have to select the network as it forgets every time the wifi card is turned off.
I have tried several steps to correct the issue including deleting all preferred networks, renewing DHCP lease.
I have reset the router several times. I cant figure this out.
Apple support refered me to Linksys support who wanted to charge me to fix the issue that they say is an Apple issue not the router.
My 2011 (Late) MacBook Pro running 10.8.3 does not have this issue. We have a HP Envy, 2 PS3's, 3 iPhones, and an iPad and all connect just fine.
Anybody having this issue? Any suggestions?