It's called blossom drop when the flowers drop off without setting fruit. It is a sign of stress in the plant, which drops the flowers to focus on survival.
There's a sticky on Blossom Drop at the top of the Tomato Forum. You just need to figure out what is stressing your plant.... too much or too little water, too hot, too much or too little fertilizer. The leaf curl is another sign of stress, so your plant is telling you it really needs help.
Here's a thread we have had recently on tomato leaf curl: