my DS went through this when his molars started to go through and I think that tooth pain is always worse at night, particularly because they have nothing else to distract them from the pain, but it may have coincided with a clingy thing and if he is feeling clingy then it will be worse if he has tooth pain and doesn't want to be left alone.
calpol was about the only thing which mad this better (and it know it is not recommended for children under 2 now but I found that I needed the calpol night)
the molars took much longer than any of his other teeth to come through and it probably didn't help that he had three molars come through at the same time. Thank goodness that he is past the half way stage now (13 down only 7 to go)
ooh I could have written this. My son is 13 months and was previously a fab sleeper, he now screams if I go anywhere near his cot. I ahve been sitting next to his cot tapping him and shhhing and this calms him down. I am not sure why he has started this, not sure if the molars are coming through or if he is protesting about his cot.
I have a sleeping bag in his room and when he wakes in the night I go in and lie on that whilst tapping!
Glad I am not the only one going through this crazy stage???