It was page #26 (@ 100 posts/ page) and must have been somewhere between post #2585 and the most recent post...#2597. I know I read that thread within the past two days and did not get that warning. Also, I have never had that warning before, ever, with any other thread or webpage for that matter. Shortly after I posted the OP, I tried the thread again, and again received the same warning. But just now, I am able to access the page without any problems. So I don't know if someone edited out an image link that was causing the trouble, or if it was, in fact, a rogue add.
Ahh, looks like you got it while I was typing my reply!
Looks like I was off a few posts too in my estimate. Thanks.