Just a thought:
Is your baby well enough rested? Sometimes babies are just overtired, especially if it is chronic, they will cry.
I highly recommend Dr. Weissbluth's book: Healthy Sleep Habits, Happy Baby. I am not a fan of the cry-it-out method that he talks about, but the book is FULL of great information for dealing with problems like yours.
Good luck and don't forget that they are always growing and changing and soon this phase will pass too!
best,
sheila