Cannot Leave Youtube Comments..?

[looobylooo]

Hi
Can anyone help please, I've tried googling for help & answers but I'm not having much luck!
~ I cannot leave comments on Youtube videos.
I click on 'leave your thoughts' to type my comment, the outline of the box turns yellow & the words 'opening..' appear in the box, and that's it, nothing else happens, it doesn't allow me to type in the box.
If anyone can help I'd very much appreciate it,
Thank you