YouTube Freezes When I play a YouTube movie even though it's completely preloaded it freezes all the time. My Flash version is updated. What should I do?

Yes, like "Ali Khan" said there are a lot of reasons out there that may cause the issue. But generally 2 categories: outdated hardware & poor system maintenance. These are manual ways to ahieve and make the PC run more smoothly, for a tech geek, it's easy; for a computer newbie, it's hard. As a result, l recommend this program to you, which can help you easily and instantly speed up your PC & fix all issues with just a few clicks. After that, see if you can play YouTube videos better than before, best regards!

YouTube freeze can happen due to many reasons. Major reasons are overload on website, simultaneous running of many programs on your computer, Low RAM, Slow internet connection or corrupt windows registry.
For smooth watching of YouTube Videos take following actions:
1. Watch videos at off peak times, if possible
2. Do not run other programs while watching videos. They slow down computer in general by making use of memory.
3. Add RAM on your computer. More RAM will make easy execution of heavy programs on your system.
4. Get better and speedy internet connection. Talk to your ISP in this regard.
5. Regularly clean windows registry. Windows registry is vital place that stores information for important computing functions. A congested or corrupted windows registry makes computer slow that causes YouTube like freezes. For this, get the best registry cleaner and optimizer. Use it once in a fortnight for fast computing to avoid YouTube freezes and system slow down.
The above guidelines allow you to take measures to and keep your Windows properly maintained.
You can get a wonderful registry cleaner and PC optimizer reginout

Perhaps there's something that is running in the background that is slowing your machine down?
Another thing that might help you is to empty your cache memory.