sharing of broadband connection ???

WHEN I ENABLE MY 2ND LAN CONNECTION TO SHARE THE BROADBAND INTERNET CONNECTION,MY BROWSER SHOWS THE MESSAGE TIMED OUT ?? AND I BECOME UNABLE TO ACCESS THE INTERNET ….AND WHEN I DISABLE THE SHARING IT WORKS VERY WELL AND FAST? WHY IS THIS HAPPENING ? I M SEEKING AN ANSWER ANS SOLUTION AS EARLY AS POSSIBLE PLZZZ HELP ME ???