Joanne,
Thanks for stopping by, I'll get right to the point. A lot of women I train do what you do; tons of cardio, ab and thigh machines. They diet like crazy and can't lose weight. The reason for this is you need to feed your body and build some serious muscle to get your metabolism going. It doesn't take a lot of work but you do have to train your entire body. Try this workout for a month.

Day 1 Chest shoulders triceps
Day 2 Back biceps abs
Day 3 Legs hips butt

Do at least two exercises for each body part 3 sets of 12 reps with a weight that is challenging you by the 8th rep. Push yourself a little harder than you have been. Decrease your cardio to 30 min. at a much higher intensity. I'm talking serious sweating.

EAT!!!! 5-6 small meals a day every 3-4 hours. For example
meal 1 high fiber cereal w/ skim milk
meal 2 soy protein shake (at least 20g protein and low carb) & 1 piece of fruit
meal 3 grilled or baked chicken breast with 1/2 c rice & 1 c steamed veggies
meal 4 soy protein shake & 1 piece of fruit
meal 5 baked fish and 2 c steamed veggies

Try all this for one week and see what a difference it makes. You'll feel lighter, more energy, and you will probably lose 2lb. Make sure to supplement with a multi vitamin, and add 1 tbsp flaxseed oil to your shakes. If you have cravings take a magnesium supplement and try green tea every now and then to boost your metabolism even more. Give it a chance for a month and I promise you that you WILL see results.