If I click to read the first post on a thread, I can usually get into the thread and read the thread (no matter the length of the thread). Once in the thread, if I use the arrows to go to the next page, it works, if I click to go to a specific page or click to go to the last page, I get the error.
If I click the view last post link to open the thread, I automatically get the error (no matter the length of the thread).