wireless problems with inspiron 1505 - no connectivity

I have a Dell Inspiron E1505 laptop that has worked fine since I got it last year. I use wireless to connect to  the internet through a router, and I also have an ethernet cord I can use if I need it - though I primarily use the wireless to allow me to move in my apartment. A few days ago my computer started giving me problems on the internet, so I rebooted it thinking it was a connecting problem. When everything loaded up again, it told me I had no wireless connection at all, and I couldn't find any networks. I called my internet provider and we verified that my internet was working just fine when the ethernet cord was connected, but when I tried to connect wirelessly, nothing worked. I called Dell and spent over 2 hours trying to fix this, including trying to install a new wireless connection, to no avail. Now when I start up it tells me I'm connected (and shows full strength to my primary internet connection) but it displays the message "limited or no connectivity" and doesn't let me load any internet pages. When I try to troubleshoot, it keeps telling me my IP address or password needs to be re-entered, which I've already done numerous times. I'm currently at a loss as to how to fix this, and I can't seem to get back in touch with Dell to troubleshoot more. Can anyone help??