I am going through this too, it takes us 2 hours to get Matilda to sleep though and she's generally up for a few hours in the middle of the night. I've phoned for help, spoken with child development people and we are going to the GP in an hour to see if there is anything else wrong.

Like the others have said, it is a developmental phase they go through at different times, the separation anxiety, the key I was told was to be consistent and comfort them but keep to a routine, in 5-10 nights things could be sorted. We have just hit our 7th night of absolute screaming...so I can't say its worked yet.