So there you are -- you've got a character who is gregarious and gets into roleplaying groups relatively easily. Your character's way of interacting with others makes it easy for other people to recognize you as a roleplayer, and even encourages them to come out and roleplay with you, even if they're not that much into roleplaying themselves. You've followed some good advice about finding roleplayers -- maybe even joined an RP guild -- and you're meeting characters you think are interesting, and you really hope they think your character is interesting too.
But then something goes wrong and you feel that special RP feeling start slipping away. The people in your guild stop talking to you as much -- sometimes the whole guild atmosphere seems to go quiet and dull, and no matter what you say, nothing seems to get the actual spirit of roleplaying flowing again. You start to think maybe your interesting character quirks aren't all that good after all. You keep trying to think of new ones, but no matter how funny your accent or entertaining your antics, people just aren't getting into it like they used to.
The problem here isn't actually you -- it's an assumption that many roleplayers, even experienced ones, sometimes have when they are in new roleplaying situations. We take the burden of creating a roleplaying atmosphere too heavily upon ourselves, when actually what we need to do is not create the atmosphere, but nurture it. Questions are the key here -- if your character has a genuine interest in other people then he or she will be able to draw out the spirit of roleplaying in them, get them talking about themselves, and start having interesting interactions together.