Congratulations on your weight loss!!
I had the same problem when I hit the 290 range also. I guess there must be something about those darn 290's. haha I decided to buy a heart rate monitor and found out I was only burning off about half of the calories I thought I was burning. I adjusted my calories to my actual exercise burned calories, and even lowered them another 100 for a few weeks for good measure. It took a couple of weeks for the weight to come off, but it did start coming off again!
Be patient and keep doing what you're doing. Your body will eventually catch up.