This is apparently a pretty common thing.
My guess would be that her new found mobility, teething, and the ability to assert her own will, or some combination of the three, are the issues you're dealing with.
Teething is an easy fix -- try the appropriate dose of Children's Tylenol or Motrin/Advil about half an hour before bed time.
Of course teething and ear infections have nearly identical symptoms. If she really is overly cranky, you might call the pediatrician and see if you can at least rule out a medical problem.
As far as her mobility and asserting her will, I'd suggest you stick to your guns about nap times and bed times. If/when she cries after you put her down, go back and check on her either every 10 min or in increasing intervals (first 5 min, then 10 min, etc.) Each time, pat and comfort her, but don't pick her up (unless she's hysterical). If she has a "lovey" or a paci, make sure she has it.
Another method I've heard about is one where you sit in the bedroom next to the crib while the baby cries, and you calm and pat her. Again, don't pick her up unless she's hysterical. Just sit there as long as it takes for her to fall asleep. Do this for 3 or 4 nights, then move your chair half way across the room for 3 or 4 nights, then move your chair next to the door, then out to the hall-way. It's about a 9-might process, but a lot of moms say they prefer being in the room with the baby rather than somewhere else in the house.
My son had similar sleep issues pop up around 6 months, and again around 8 or 9 months. I used both methods and each time it took 2 -3 nights to get him back on track.
Good luck!