My 5 year old has insomnia???

Is this possible?  Can a 5 year old suffer from Insomnia?  I have not gotten a diagnosis from her pediatrician yet but I am at a loss for what could be keeping Jenna up every night till 11!  We have a had her on a 730-8pm bedtime every night since she was born and she hasn't had much of a problem with it.  Of course, during the summer we keep her up a little bit later each night but I can't, for the life of me, figure out why, all of the sudden, she can't seem to fall asleep till 11.  I thought it was the allergy medicine but I switched her to the 12 hour medicine and I give it to her in the morning AND she hasn't had it in 2 days!  In the past 2 weeks, she has put ME to bed a couple of times.  I am hoping that with her being back at school today after a week of Spring Break, she will go to sleep in a heartbeat tonight.  Fingers crossed...