When did Raj start being able to talk in the presence of women without the need for alcohol consumption?
In Season 2, Episode 17 The Terminator Decoupling, it was shown that Raj could perfectly talk to women and be flirtatious without consuming alcohol. But Raj is shy and believes that He could only talk to women when he's drunk.
In this episode, the four guys are on a train traveling and they meet "Terminator: The Sarah Connor Chronicles" fame Summer Glau and as usual, Leonard and Howard starts hitting on her and Raj could only do it if he consumes alcohol, so he goes and fetches a bottle. Then the conversation among Leonard, Howard and Sheldon happens like this.
-Normally around women, he has the personality of a boiled potato.
-Put one beer in him, and he's M. Night Charmalarmalon.
-Is that what he's drinking?
-It's not even real beer.
-What? - Look at it. Non-alcoholic beer.
-Some sort of placebo effect, I guess.
Technically this is the first episode where we audience and Raj's friends get to know that Raj could talk to women without the need of alcohol.
But if Placebo effect doesn't count, as pointed out in the comment, Raj was 'cured' in the season 6 finale: The Bon Voyage Reaction.