Thread width

Hi all, I am looking for a pointer as to where I have gone wrong. I have obviously altered some code somewhere but am at a loss as to where to start looking

I manage 2 forums that work pretty much the same way. In one, the width of the posts is fine and conforms with the rest of the forum. In the other though, the width of the posts is halved, and while the rest of the forum is ok, the posts themselves are narrow (please see images)

I might assume the issue in is post.php but I was wondering if someone could point me in th eright direction please.

Cheers

Richard

Normal width

Abnormal Width