It's been many years since your post, but for future users this worked for me.
I have a a Brother MFC-7840W and recently purchased a Verizon router MI424WR (newest generation). We had problems setting up a wireless Brother connection with the previous Verizon router as well.
I easily connected wirelessly to our 2 Windows-based laptops and to our HP color printer. The problem was connecting to the Brother wireless printer.
Here's what finally worked for us:
1. Reboot the Brother printer (that is, get back to the original factory settings).
2. The "SecureEasySetup" didn't work, so we had to use the Brother "Setup Wizard."
3. Choose the correct SSID.
4. Choose authentication "WPA/WPA2-PSK"
5. Choose "AES"
6. Enter your 16 digit WEP key.
7. You should get a "connection" message on your Brother.
8. I still couldn't print, so I..
9. Went into my PC's "Control Panel" and chose "Devices and Printers".
10. REMOVE any Brother printers, then choose "Add a printer" to add back the Brother!!
11. Then we turned the Brother off then back on..and
12. Voila, we could print wirelessly.
Hope this helps. It was very frustrating to say the least. Thank goodness I have a genius wife.