Besides the type of security protocol being used which must match exactly between it and the router, so must all of the wireless settings match including whatever the wireless password is that the router is currently using.
First, remove all security off the router. Now try to connect to your SSID with no security temporarily. If connected and verified, go back and add your security WPA2-AES with your passcode. Make sure your MAC filter is off.
I had same problem, and no matter how many times I told it to "forget" the connection, scan, and create a new connection it would respond with "invalid password" (error response overlays the typing area so hard to see).
I did as sabretooth suggested and changed security to NONE, connected my Galaxy, went back into router config and changed back to WPA/WPA2-PSK (TKIP/AES) and set network password. Disconnected Galaxy, re-scanned, connected, and gave password --- and it worked.
Puzzling why it didn't work before as I had security and password set the same.
An update on my earlier post... After finally getting my phone connected it later disconnected and refused to re-connect, even using the procedure sabretooth suggested.
After hours of trial and error, calling the helpless desk (who wanted to charge me $40 + $9.99/month before they would give me tech help on my NEW router/modem), and doing every search I could think of, I finally found the "real" problem (for me at least).
The Comcast (Xfinity) modem/router combination is limited to FIVE (5) wireless connections!! Of course this isn't documented anywhere.
My solution was to re-install the Linksys router this router/modem combo was supposed to replace, and plug it into one of 4 Ethernet ports on back of new router/modem. I'm sure something will go bad, but for now I can connect all my devices: DirecTV whole home ring (2 DVRs, 2 receivers), 3 computers, 2 Galaxy SIII cell phones, Tablet, and 2 Nooks.
My solution was to re-install the Linksys router this router/modem combo was supposed to replace, and plug it into one of 4 Ethernet ports on back of new router/modem.
FWIW, if you have done this then you actually should have the CC supplied gateway device put in to *bridge mode* by them so that it becomes a plain vanilla cable modem. Cascading two routing devices results in a double NAT condition (Google for info) which can cause some issues for your home network.
Absolutely right! As soon as I deleted some devices, my smartphone showed up as connected. I just got CC's modem/router. Fortunately it can be returned. I will get a different router/modem that accepts more devices. TY