Did it work normally before? If so, what changed?
You may open cmd as administrator and run the commands below, then restart your system.
Netsh int ip reset
Netsh winsock reset
How to reset Internet Protocol (TCP/IP)
http://support.microsoft.com/kb/299357/en
Please check the articles below for other recommended troubleshooting steps:
How do I improve my 802.11n wireless performance?
http://www.intel.com/support/wireless/wlan/4965agn/sb/CS-028449.htm
Access Point (AP) firmware updates may resolve wireless network issues
http://www.intel.com/support/wireless/wlan/sb/CS-006321.htm
NOTE: These links are being offered for your convenience and should not be viewed as an endorsement by Intel of the content, products, or services offered there.