It is a good idea to reset your unit back to factory settings and clear out any glitches that may have developed in the unit. (Especially if you are starting to experience problems that were not there before).
Performing a factory reset will clear out any settings you may have changed or setup (SSID wireless name/password, parental controls, firewall rules, etc.)
You should backup your settings before you do this. Instructions HERE
FACTORY RESET (or "HARD RESET"):
1. Make sure the power to your unit is ON
2. Disconnect the Coaxial cable in the back of your modem
3. Use a straightened paperclip, tip of a ballpoint pen, or push pin
In the back of your unit is a RESET hole
4. Locate the RESET hole, located in the back of your device.
5. Push the RESET hole in for 25 seconds, then let go
6. Wait for the unit to reboot, and reconnect. You will see the lights starting to come back up on the front of the unit
If you saved a copy of your settings configuration, load your backup configuration file now.