|As it is stopping awaiting buffering it implies that, at times, the information in the buffer is being emptied at a higher rate than it is being filled. This would point to the download being slow or erratic which is why I wondered about the internet.|
If you google around there are several websites that check your download speed. It could be your phone line or a server problem. See if unplugging all phones makes any difference. It might be worth a call to your server technical support.
I can't think of anything to do with the computer itself which would fit these symptoms, except perhaps a modem problem.