sudden separation anxiety in 4 year old

[middles]

My 4 year old daugther is in pre-kindergarten.  Prior to pre-k, she attended preschool and summer camp in the same facility.  However, recently she has been suffering from separation anxiety.  This all started when I registered her in several extracirricular activities.  First she started dance classes (once every week).  It went fine for the first 2-3 weeks, but by the 4th week, in the middle of the session, she came out and refused to go back in.  I asked her what was the matter and she just said that the music was too loud and there were too many mirrors in the room.  After that, she refused to go back to dance class.  At the same time that I enlisted her in dance classes, I also enrolled her in gymnastics class.  The first 2 sessions went well, but after that, she refused to join the other girls in the activities.  Whenever I ask her what was the matter, she just says that she's scared of the teachers.  All the activities are performed within view of the parents.  Everytime we go to gymnastics, she gets anxious and refuses to go in with the other children and she just wants to sit next to me and watch the other children.  So now, I have stopped both gymnastics and dance classes.  I have, however, enrolled her in a cheerleading class in the same facility as her pre-k, thinking that maybe someplace familiar would be more comforting to her.  That didn't work.  The first time I took her to cheerleading, she cried for the first 20 minutes and then eventually joined the other girls.  The worst part is, the next time she went back to pre-k, she cried when she got to school (something she has never done before - not in preschool, summer camp or beginning of pre-k).  It has been 2 weeks since she first cried at pre-k (only crying for a couple of minutes when I drop her off and the teachers tell me she's fine after I leave).  I don't know what might have caused her SUDDEN separation anxiety.  Maybe a couple of other facts might help.  She has had a couple of changes in teachers in her pre-k.  There are usually 2 teachers in the class.  One teacher has been the same since preschool.  However the other teacher has been changed a number of times.  When she first started dance class, there was only one teacher and after 2 weeks into the class, another teacher was introduced into the class.  I am thinking that the introduction and deletion of these teachers might be a factor in her anxiety.  She is always telling me that she will miss me and that she just wants to stay home with me.  I try to confirm to her that I will always be there to pick her up and that there is nothing to be scared of, but it obviously doesn't help.  Help, any ideas or suggestions on what I should do???