It won't like me on my account or watch any videos on Youtube

If "your browser sent a request that this server could not understand"
and "size of request header field exceeds server limit", your request
is a bad or oversized cookie. (The same thing is true for "Error 400").

For some very strange reason, it seems 9 of
10 Bad Request messages implicate Firefox.

Simply delete your "Cookies" and everything
will be okay. Don't worry about erasing them;
nothing bad will happen. You won't lose your
internet browser's "Bookmarks" or "Favorites".
The worst thing that could happen is you will
be asked to retype your username/password
when you return to YouTube and some other
websites -- that's all.

As you're dumping your cookies, you should
also erase all your "Temporary Internet Files"
and "History". This will render your computer
totally "fresh" in YouTube's eyes. It would be
best if you shutdown / reboot after doing this:

Internet Explorer 6:
> Tools > Internet Options
> Delete Cookies > OK
> Delete Files > OK
> Clear History > Yes
> OK

Internet Explorer 7:
> Tools > Internet Options > Delete...
> Delete files > Yes
> Delete cookies > OK
> Delete history > OK
> Close (browsing history window)
> OK

Peace,
B