|Use Windows rather than Intel PROset Utility to manage your internet connectivity.|
A lot of the Dell Inspirons come with Inter PROset wireless cards and along with the driver they install the Intel PROset wireless utility to enable you to connect to the Internet. Some routers appear to have problems with this. My daughter had a similar problem on her Inspiron 640M with her Virgin supplied D-Link router. I resolved her problem by using the Windows built in Wireless Zero Configuration (WZC) utility.
Try to use the Windows built in Wireless Zero Configuration (WZC) utility for your internet access instead of the proprietary Intel PROset wireless utility.
To use WZC uninstall the Intel PROset Utility. This may also uninstall the driver as well as that is how some uninstallers are designed.
If it does uninstall the driver as well, then install using the Intel PROset wireless utitlity install disk/file but only install the driver and NOT the utility. If there is no driver only install option, you may be able to manually install the driver (as I did) by browsing to and selecting the driver only as part of the driver update process in device manager.
You should find then (assuming no hardware problems) windows will report that there are available wireless networks and you will see a wireless icon in the task tray.
Opening it up will reveal the wireless networks in your neighbourhoood. Select yours, provide the encryption key if one is required and you should be able to connect.
Hope it helps
☺ When everything else fails, read the instructions.