No, this is a terrible sign. Dudes are simple but can sometimes send confusing signals. If he is normally sweet to you then one day turns rude, it means he no longer likes you. By the same token, if he normally teases you and all of a sudden starts treating you with respect, he is not interested in you anymore.
When you see 180 degree behavior, especially from "piggy-tail pulling" to kindness--watch out--he's probably moving on.
You can save this one though, completely stop responding to his communications and generally follow my instructions from a question I recently answered: How do you get a guy to like you? He'll come running back--trust me!
uh, you need to meet this guy face to face and see what his deal is before you make any further decisions about him. simply put: try a date.
What if the guy is usually a shy guy who seems to have a "whatever" attitude towards you and then suddenly becomes super sweet? This is another type of 180, but does this mean he's interested or maybe he's just gotten to know me well enough that he doesnt feel shy anymore?
I disagree with Mystery Man. Him calling you "Lady Friend" could be good or could be bad. But, it definitely means something. Because any noticeable change in interactions with someone else means that there is a change in the relationship as well (though it can be difficult to know what that is).
As for "Lady Friend":
The good interpretation - The guy isn't sure where your relationship stands, and so he is testing out how close he can get to calling you "Girlfriend".
The bad interpretation - He just thinks of you as a friend now, and wants to call you something that is distinctly not "Girl Friend".
Either way, this is a situation that calls for face to face communication. If you feel comfortable with it, ask him out on a date.
Oh, and Super Woman, yet again there are two interpretations that I can see for this guy becoming sweet:
The good interpretation - He feels like he got a green light from you and he is turning on the charm.
The bad interpretation - His "whatever" attitude was in place when he was trying to look cool for you, to get you interested. But, now he just thinks of you as a friend and so no longer is playing it cool.
There are a million interpretations for human behavior, and disecting it will only lead to worry. If you like the guy, pursue. If you don't like him, don't pursue and assume he's not interested until he proves otherwise.