|Try recycling the power on your router/access point. Simply unplug it, leave it powered off for about 10 seconds, then power it back up and see if you can't login to your wireless network now.|
If that doesn't work, delete the existing wireless profile for that WLAN and reconnect making sure to enter the encryption key correctly.
If that doesn't work, try resetting the encryption key for your WLAN and then attempt to reconnect.
If that doesn't fix the issue, try resetting the router to factory defaults (info on how to do that is in the manual/user guide that came with the unit) and reconfigure it.
If none of the above works, and your device can connect to other WLAN's, it could be time to replace your router.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.