lurk's question, while flawed, is typical of some newly exited who still hold on to the belief that "The Truth" really was the truth until it got off track. So I think he/she's wondering when we saw the wheels started to come off the Society's "chariot."
And the answer to that is: It depends on when you became a dub, how long you were in, and which segment of JW history you were a "witness" to.
Many of us were true believers at some point, to some extent. Then we stopped believing. For me, that was when dubs stopped being "God's People" and became just another religion at best, a cult at worst. I'd date my own personal revelation at 1990 due to some things I saw happen in the organization then that caused me to doubt. The nail in the coffin was 1995, when the central teaching on "this generation" was tossed aside with a lame explanation and almost no visible reaction from the rank and file. Even then, it took me several more years to walk away; that's how powerful a hold this cult has on its members.
So, that's me; someone else's mileage may vary.