I went to the website that was posted. I have been entering the 10-digit security key so I haven't lost it. I logged into the Linksys router to doublecheck and I've been entering the correct key for key 1, consisting of various 10 letters and numbers, and using all caps as displayed on the router page. This is the same key I've used to connect every item to the network and it's worked for everything else. I've left the CCK setup to check all keys, then listed key 1 specifically to match the router page and neither of those options worked. I even tried entering the other three keys listed (for keys 2 through 4 on the router page) even though key 1 is selected in the router setup.
But I'm still willing to try anything at this point!