Cant connect to internet

delete/forget the wifi connection in the tablet. re do the wifi set up with the proper WEP/WPA password from the router.

Authentication errors happen when the tablet does not have the correct credentials to log onto the network. Be sure you have the correct SSID and password to join your local network. You can check this in Settings.

because the WPA is a protection of the wi-fi LAN where you are trying to attach

http://en.wikipedia.org/wiki/Wi-Fi_Protected_Access

How many 'bars' are showing on wi-fi signal strength indicator (presuming you are using wi-fi for internet access)? If the signal strength is low, you could be losing connections that way, or there might be interference on the wi-fi channel that the tablet is using. Try changing channels in your wi-fi setup and see if there is an improvement in the behavior.

Solution 1.Check wireless connection.
The first step of diagnosis have to any other device connected to the same network, ensure the wireless connection is working fine, or verify the settings of your wireless router to correct it.
2.Check your Keep Wi-Fi on during sleep Settings.
Owing to Wi-Fi sleep policy your Wi-Fi connection may be going to get disconnected every now and then.
Tweak this policy to keep your Wi-Fi connection awake.
[Settings] >>[Wi-Fi]>>[Advanced]>> Check [Always] to keep the Wi-Fi on during sleep.
Save changes and exit all the screens. Your Wi-Fi will never get disconnected again due to this policy.

3.Check signal strength of wireless connection.
The performance of a wireless network connection depends in part on signal strength.
You have to connect the Wireless network where the signal strength is strong.
Check Wireless network signal strength icons in notification bar.

4.Try to turn off/on Wi-Fi on the device.
First to turn off Wi-Fi, [Settings]>>[Wi-Fi] >>[turn Wi-Fi to off].
And then to turn on Wi-Fi, [Settings]>>[Wi-Fi]>>[turn Wi-Fi to on].

5.Try to forget network on the device.
Forgetting wireless networks allow your tablet/phone to reset some settings.
[Settings]>>[Wi-Fi]>>Press & hold your[Net Work Name(SSID)]for 2 seconds.
>>Select[Forget Network]>>Re-Connect your wireless networks if it's disconnected.

6.Try to reboot your device.
7.Make sure your firmware is up-to-date.
>>Select[Settings]>>[About tablet]>>[System Firmware Update]>>[Check Update].

8.Try to reset your device.
Note: once RESET was performed, all data, apps, settings and personal information will be deleted after initialization.
Third-party programs might be the major probability of Tablet/Phone instable, suggested to have a full reset for the device if the situation persists.
[Settings]>>[Backup&reset]>>[Factory data reset]

9.Try to other wireless connections.
If steps above were not able to solve internet connection problem still, please try other wireless connections if available, otherwise contact your networking provider to technical support.

trying dumbing down the authentication on your wifi router. Try these:
turn off 40mhz wide channels
try wpa instead of wpa2
try tkip instead of aes

if all else fails, try wep.

Need To Double Check Password And Connection Info. One Error Sets The Whole Thing Off As Wrong.

You may have a connection to your network already saved. Go into settings > wireless. Tap and hold on your network and select "Forget Network". Also note that if you have only WPS or a pin for authentication to your network this will not work on a tablet. You need to enabled WEP, WPA, or WPA2 with a password

Step 1: Remove any old connections in the Tablet by Long Press Forget Connection
Step 2: Reboot your Wireless Router
Step 3: Attempt to connect again
Step 4: If this fails, log into the Wireless router and charge the authentication mode from whatever you have now to WPA Personal and enter a Passphrase you can remember
Step 5: Connect to your Wireless using the new Passphrase