This is most likely an internet connection speed issue. Take the speed test. See if selecting the medium or low resolution option helps.
Be sure you have the latest version of Adobe Flash installed.
DVR recorded content is less sensitive to network speed. If your DVR'd content plays back smoother than live, it is most likely a bandwidth issue.
Try rebooting your computer. Running a computer or laptop for long periods without a reboot can cause Windows to run inefficiently.
If you are on a paid plan and are not satisfied, you may request a refund.