This user apparently has the same problem as I.
I tried completely replacing the single.php with default code and this problem is still occuring. The dilemma is strange as I haven't been playing with any code for months and suddenly this happened— so I'm starting to think it's a server side issue (host is mediatemple). Here's an example below. The repeat of content occurs on every single post but not on the index page. Any ideas anyone? All help is much appreciated, thanks in advance.