Are you sure you are entering the correct password for your network? If not, all it takes is a typo, and it will keep you out. Also, it is possible that you or someone else changed the settings in the modem to block the device (it happens). If neither of these, try the following and see if it helps.
Try this....
1. Go to "Control Panel".
2. Next go to "Network and Internet" and then "Network and Sharing".
3. Now click on "Manage Wireless Networks".
4. On this screen, remove all wireless connections by "right clicking" on it and select "Remove network" from the drop down menu.
5. After doing this, close the open windows and reboot the computer.
6. Once the computer is fully reloaded, scan for the "WiFi networks".
7. Click on...