I had been having this issue for a while before I finally figured how to solve this problem.Since I am a tech expert all i had to do was google the right keyword and find out what was wrong.Here are some possible potential solutions that you should try.

If you are running windows Vista then just diagonize the connection and it will tell you the reason why it is not connected.

Solutions 1

I had this same problem and I found some software on line that fixes the problem. My problem occured after I ran AdAware on my laptop trying to clean it up. I had no DNS server and my IP address read as 0.0.0.0. When I did a ipconfig /release, I received a media is disconnected error. I am a software developer so I knew exactly what to type in google to find the solution to this problem. I only had the problem for one day, and I know of people that have had this problem for months.

I found a website that offers a freeware software download called WinSockFix.exe, which you can also type in google for a search. The URL ishttp://www.tacktech.com/display.cfm?ttid=257.

I had to download this of course at work and burn it on a CD. If you have a floppy drive it is small enough to fit there, or if you have a USB key. At any rate, I got home yesterday, popped in the CD, and after less then a minute and a reboot. My issue was completely resolved. After my refresh, I no longer received the “Limited or No Connectivity” on my wireless signal and I instantly clicked on IE and it opened right back up like nothing had ever went wrong.

Solution 2
TCP/IP stack repair options for use with Windows XP with SP2.

For these commands, Start, Run, CMD to open a command prompt.

Reset WINSOCK entries to installation defaults: netsh winsock reset catalog

Reset TCP/IP stack to installation defaults. netsh int ip reset reset.log

Reboot the machine.

Solution 3
Solution 4
1. Go to the control panel & select “Administrative Tools”.

2. In Administrative Tools, go to “Services”.

3. On the Services screen, scroll down until you find “Wireless Zero Configuration”.

4. Start this service.

5. Now go to “Network Connections” and right click your wireless adapter icon.

6. I can’t remember exactly which tab it is, but find the one where you have the option
to check or uncheck “Use Windows to configure my wireless connections” or something to that effect. Make sure it is checked.

Solution 5
Check your WEP key ? Did you reset your router in that case your wireless configuration key would have changed as well.
Login at 192.168.0.1(type the number in your browser – firefox/Ie and put in username and password) and change your WEP key.
Also try
1) Verify what kind of wireless card/adapter you have: a, b, g, b/g/a, N, etc.
2) Check the broadcast mode on your router. If you have a “wireless-b” card, you need to be broadcasting in either “b-only”, “mixed b/g”, or “mixed” mode. Note: Sometimes the “mixed” modes don’t work; and to support a “b” card, for example, you might have to broadcast in “b-only”. Try each of the applicable possibilities until you get the highest common denominator that works on all of your wireless devices.
3) If there are several wireless signals within range, make sure interference is not causing problems. If you see several signals in the available networks list, I would suggest changing the channel to something other than 6 (the default) on both the router and wireless adapter and making sure you have a unique ssid (in case your neighbor has the exact same router).
4) If your laptop/PC still doesn’t automatically connect, refresh the list of networks and try the usual steps. It should now work.