46,107.

Here's one with 196,051 posts (4.25 times more than our World Record Thread): http://www.techimo.com/forum/showthread.php?t=144659

I am unsure whether all of the replies are legitimate, or if they have used bots. The forum has 221,033 members (13.12 times more than us), so perhaps it is.

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram