Has your daughter recently gotten more mobile -- more rolling over, scooting around? When my son was at that stage, we had a period of about 2 weeks where just about every other night, he would wake up (after sleeping through the night since 3 months old) with crying jags that lasted up to 3 hours. We took turns going in to soothe him by rubbing him gently or talking to him quietly. Some nights, though, even this didn't work and we even tried rocking him to sleep (a practice we had really worked hard never to let become a habit), but he'd wake up as soon as you tried to put him back in the crib. Nevertheless, it passed in a couple weeks, and he went back to sleeping through the night. Remember, though, that cry it out doesn't mean you don't respond to your baby at all. Go in, meet her needs as best you can (soothe), then give a little time (anywhere from 2-5 minutes). If she's still crying, return, soothe, give a little more time (4-10 minutes). We found, though, that sometimes we really just needed to give him some time to cry (it's a self-soothing mechanism for babies), while at the same time, making sure he knew we were still there by going in periodically to calm him down.