C.S.
Perfectly normal! That's what happened with my 3.5 yr old toddler. He was a fantastic sleeper who went to bed with absolutely no problems until 3 months ago and then, poof, he began dragging his feet. All of his friends are the same way so at least, I know he's normal:)
For some of his friends, a goal chart seems to work. They have printable ones at the chuck e cheese website where you can get free tokens if you meet the goal. For my kid, he is motivated by bob the builder dvds so we tell him that he can watch xx number of episodes the next day if he goes to bed at nis regular bedtime. But yes, it is hard. I find that I have my husband put him to bed (without my help) about 1/2 the nights just so I can get away or have my time to myself. He has more patience with things at night than I do. Probably because I'm a SAHM.