If you use a wireless access point or wireless router to access the Internet with a laptop, then the wireless connection might be the cause of your problem. You may have to use a wired connection to your network until the wireless problem is solved. You'll also want to have a copy of your wireless access point or router's user manual nearby.
There are two main potential issues with wireless connections: configuration problems and security problems. Consult the user manual to see how to access the wireless device -- this is usually done by typing the device's IP address into a Web browser. From there, you'll need to check the manual to find the proper settings. You'll probably have to call your Internet service provider (ISP) for assistance, because the necessary configuration will vary tremendously depending on the type of network you have and the type of connection provided by your ISP.
The wireless device's security settings could also be causing problems. You can access these settings the same way you accessed the configuration. If you have a wireless security protocol enabled, you won't be able to access the wireless device without using the proper password. You can set and reset the password the same way you can change the other settings.
If none of these steps have solved your connection problem, there are still a few last-ditch efforts you can attempt.