I've been having the exact same problems and in the last couple of days if I put a search in their search box it freezes for ages, it seems to be at random intervals and randomly on other web browsers.
What I have noticed though is that they seem to be updating or have updated parts of their website, the layout seems to have changed and they maybe updating their software which could be the factor in why some people are having problems with youtube and hopefully all will be sorted out soon.
Also to make sure it is not a problem with your flash player or java try going to another site and try their videos out, places like veoh and liveleak are trusted sites and if they work it will most likely be a youtube problem.