Freezing, slow pausing between frames, etc. are most likely caused by outdated Flash player or a browser issue.
It would be best to update Flash Player, clear all browser caches, and restart the browser completely.
Flash can be updated here (uncheck the “optional offers” so you don’t get unwanted software):
If the above steps don’t help, try using a different browser, and make sure all latest OS (Windows/Mac) updates are installed.
If the problem persists, there may be a software conflict or hardware issue, and the computer might need technical support from an administrator.