I'm sorry but this is not enough information for anyone to be able to help you.
Please provide some more details: Is it all videos or just some and please name which ones? What operating system and web browser are you using? Is this a desktop, notebook or tablet? Are you connected by ethernet cable (hard wired) or are you connecting wirelessly? Are you using the latest version of Flash, you can check your version and what the latest available version for your browser is by going here: http://www.adobe.com/software/flash/about/ Have you tried to power cycle your modem and router?
- Norm