I run 2 - 3 times per week, mostly on the treadmill this time of year. Like you, the only thing that really seems to get the fat off is running combined with strength training. I usually cross train with Imax and Imax2. I have used both of these workouts in place of speed work when preparing for a race. I hate to do sprint work on a track, so both Imax workouts were fairly good substitutes.
Occasionally I will throw in some kickboxing, just to really get the effect of cross training, but my long-term rotation looks something like this (depending on if I am trainign for a race):
Mon: Run 5 miles plus abs
Tues: Imax or Imax 2
Wed: L&G and PUB
Thur: Off
Fri: Run 5 miles plus abs
Sat: Run 5 miles or other cardio
Sun: ME
This is what has worked for me for quite a while and I am too scared to change my rotation.
Best of Luck,
Tina