trekkie1701E said:
I was referring to the Klingons in Enterprsise, not DS9. Remember, Enterprise takes place thirty years before Kirk & crew.
Well, you just have to use your head and think of a decent excuse.
The real reason they didn't go back to the ridge-less look is because they felt it looked stupid, and make-up techniques have improved drastically.
Besides, the Original Series Klingons were supposed to have the ridged foreheads, there just wasn't enough money in the show's budget. So, if you'll look closely to pictures of the original Klingons, you CAN see small ridges painted on. It's not very obvious, but they're there on some of the Klingons.
As far as timeline's concerned, there are a lot of explanations that can be used:
The Klingons from The Original Series absolutely hated humans. They may have surgically-altered their appearance for the purposes of espionage.
In the Deep Space Nine episode "Trials and Tribblations", Odo exclaims "Those are Klingons?" (refering to the ridge-less Klingons). Worf states "We don't like to talk about it." This could indicate that something happened to the Klingons during that period that changed their appearance.
Or, my explanation. The Klingons offended Q, and so cursed them with a temporary change.
Whatever you pick, there you go...