The Problem: The reason why you are speechless when you approach girls now..is because of approach anxiety returning in full swing. You probably don't approach girls now as much as you used to, when you didn't have this issue. You're probably usually thinking negative thoughts like; "She might reject me"..shoving you into your own head before you even open your mouth.
The Solution: Stop thinking "She might reject me" every time you approach. Get rid of those negative, outcome dependent, thought pattern loops. Reward yourself just for approaching her in that type of situation. "That was an awesome approach..who else would have the balls to do this. I'm so awesome!!!". Also..approach more girls consistently, and approach them in awkward situations - for an example: approach a hot girl in the line at the store, and stay in that situation for a couple of minutes, while everyone is watching you. It will get awkward, but it's supposed to be. That's the whole point..You're stretching out your comfort zone, by proactively numbing yourself to that social pressure looming over you. Most guys will not take my advice anyway, and won't do this because they seek to avoid that social pressure at all cost. The reason why you have approach anxiety or why you don't know what to say to her (speechless)..is because of the very social pressure that you are trying to avoid by not approaching girls as soon as you see them (the 3 second rule applies here)..followed by sitting in that uncomfortable situation for a while, and say anything that pops up in your mind. You've probably been doing the opposite..and trying to come up with the politically correct, low-risk words to say to her..to keep her from walking away. And i got news for you my friend..game doesn't work that way. In this game..It's..high risk, high reward!
You can still approach girls in normal situations too like: a close proximity indirect approach, when the girl is by herself. Again..approach girls in high social pressure situations, stay in set as long as you can, and say anything that comes to your mind in the moment (ie free association). Even if you are nervous, and even if what you're saying to her doesn't make any sense. Over time..you will feel more comfortable talking to girls in any situation..even the real hot ones. And your words will come through fluently..without you even having to think of what to say to her next.
I've experienced a lack of approach anxiety recently because of this exact regimen. Personally, i do 1 to 2 of these type of approaches a day, whenever i'm out running errands or going about my daily life.
LEARNING GAME IS LAME!..Right up until the point when you will eventually see a hot girl standing or sitting right in front of you. In that moment..you will wish that you had learned game!