1st of all make sure u got the latest driver for your wireless go to start computer system properties device manager and check for and yellow exclamation marks u could downlaod latest driver from website
www.dell.com/support if this all fails then try
please take a look at the below forum discussion link where the same issue is been discussed.
http://social.answers.microsoft.com...k/thread/e834b67f-12ae-4b3c-aa13-af27553350bd
This issue may occur if the Enable IEEE 802.1X authentication for this network check box is selected. If this check box is selected, but there is no server to authenticate against, the connection is disconnected. If you reestablish the wireless network connection, it disconnects again after a short time.
Method 1: Disable IEEE 802.1X authentication
To disable IEEE 802.1X authentication, follow these steps:
Click Start, type ncpa.cpl, and then hit Enter.
Right-click your wireless network connection, and then click Properties.
Click the Wireless Networks tab.
Under Preferred networks, click your wireless network, and then click Properties.
Click the Authentication tab, click to clear the Enable IEEE 802.1X authentication for this network check box, and then click OK two times.
Method 2: Remove and re-create the wireless network connection
To remove and re-create the wireless network connection, follow these steps:
Click Start, type ncpa.cpl, and then hit Enter.
Right-click your wireless network connection, and then click Properties.
Click the Wireless Networks tab.
Under Preferred networks, click your wireless network, and then click Remove.
Click View Wireless Networks.
Under Network Tasks, click Refresh Network List.
Under Choose a wireless network, click the wireless network to which you want to connect, and then click Connect.
Also I would recommend you to update the network adapter drivers and check.
Regards,