You need to diagnose where the bottleneck could be before concluding it is your computer. The bad news it takes a bit of time and technical know how to work through and identify where the issue is located. I have assumed you have a Windows based computer.
Others have suggested doing a check and clean out of viruses and malware which is a good first step but it may not fix the problem.
If your computer functions satisfactory with non-internet based applications such as Word Pad, then I would say your computer is fine. The bottleneck is somewhere else.
A simple thing to try is to replace the Ethernet cable (that's the cable used to connect your computer to the Motorola modem) in case it has been damaged and isn't connecting cleanly.
You can try to turn off any 3rd party firewalls (except for Microsoft's Firewall), anti-viruses, anti-spyware software running in the background if they have been installed and commenced automatically on start-up.
These type of programs are known to slow down and even block access to the Internet if they have not been configured correctly.
If you don't have any of the above mentioned 3rd party products, then check to see that Microsoft's Firewall is configured to allow an internet connection from your modem\router.
You can also do a thorough speed test of the internet connection that will also be useful. I suggest you download and install NET Traffic Meter 2.1.2567 from http://www.softpedia.com/ which is free. NET Traffic Meter is a piece of software that monitors the traffic on a network or modem interface. It includes features to monitor your data volume, download and upload speeds, and can measure the specifications of your internet interface. You can then compare these with those sold by CHARTER.
Another issue could be that your web browser has been corrupted and may need to be reinstalled.
From a hardware perspective your Motorola surfboard modem could be damaged or your Ethernet network card in your computer could be misconfigured or damaged. If the network card is misconfigured it can be configured from Windows control panel. If the modem or the network card are damaged, you would need to replace them.
If you are not technically knowledgeable about computers and networks ask a geek friend to help you out otherwise do some research online to help you with network configuration and firewalls.
I have included a few resources at the end that may help you with your troubleshooting.