Wifi connection password error -- please help!

I'm attempting to connect my new white iPhone 4 to my Wifi network, and it keeps saying that the password is incorrect when I am 100% entirely sure that I'm typing it correctly. I previously had a iPhone 3GS which still connects (with the same password). I just reentered the password on that device, and it connects immediately. My Mac Pro is also connected via the same wifi connection and the same password. But for some reason, my new iPhone 4 will not connect.

I've tried:

• Typing the password 10 times. Ensuring that all letters are correctly typed and that case-sensitivity is correct.
• Resetting the phone and trying again.
• I opened Keychain Access on my Mac Pro, opened the Wifi key, copied that, pasted it into an email which I opened on the phone. Copied and pasted that into the password box, and it's STILL not working.
• Upgraded the phone and my Airport Express to the latest firmware.

Any ideas? I'm wracking my brain but can't imagine why this would not be working...

-Brian