When Cry it Out Doesn't Work...

I haven't written a post about Savannah's sleep in awhile. That's because after a little bit of sleep training when she was five months old, she had been sleeping great! Two naps a day, at 9 and 1, that usually last between 1.5 and 2 hours each. She also settled nicely into a six o'clock bedtime, and slept mostly through the night. I was a happy mama. Lately, though, we're having a bit of a sleep issue over here, and I'm just not sure how to fix it.
From the time she was 5 months until she was 8 months, she would go to sleep at night, wake up at 4 for a brief feed (I would take her to my bed, nurse her, and then put her back in her crib where she would go back to sleep right away), and then sleep until 7 or so. At 8 months old she weaned herself to a bottle and continued to wake for a feed around 4. I had in mind to continue allowing the early morning feed until 9 months of age (following Dr. Weissbluth's advice from his book Healthy Sleep Habits, Happy Child), so I would go into her room and give her a bottle at that time. This was when the trouble began. She began not going back to sleep after her bottle, but instead stayed in her bed playing or fussing.
Consulting my book again, I decided that it was time to stop the early morning feed. By this time, she was also nearly nine months old. I decided that I would stop going to her when she woke around 4 and instead let her cry it out until she learned to stay asleep in her bed until morning. After a few nights of this, it seemed to be working, as we had a few successful nights. But then she started waking at 4 again. And then staying awake. Or she wouldn't wake at 4, but would wake at 5 or 5:30 to start the day. Here and there we would have a few good nights, but mostly not. Over the summer we tried a later bedtime, at 7, for about a month. At first this seemed to work, as she slept until at least 6:30 or so in the morning. But then again, she began waking too early. Each time I would let her talk/fuss/cry herself back to sleep. If she woke before 5, it would usually last for an hour and then she would fall asleep again for an hour. If she woke after 5, she usually wouldn't go back to sleep. She seemed terribly tired and fussy in the evening. So I went back to a bedtime at 6, but the problem continues.
Lately it's been worse than ever. She is crying harder and longer. I feel like cry it out is failing me. The more weeks that go by where I make her lay in there and cry, the harder the crying gets and the more frantic she becomes. The last two mornings we've been woken at 4 for the day, and I'll admit, both times I have eventually gone in with a bottle (after an hour or more of crying.) She clings to my neck when I get her and acts scared.
I have a feeling part of this is separation anxiety; when she wakes up in the early morning and I'm not there, she gets upset and instead of rolling over and going back to sleep, she fully wakens and begins to cry for me. What I don't understand is why cry it out isn't working. She also seems to be starting to have trouble falling asleep or staying asleep at nap time, and I know this fragmented nighttime sleep is to blame. I think we may go back to a later bedtime again and see if maybe this will help her sleep until at least 5/5:30 instead of 4. If you made it this far into my incredibly long and rambling post, I'll keep you posted on how things go from here! ;-)