I'd say, do it.
I started running in January 09, for the reasons you mentioned. First, on the treadmill, then outside. I really liked it, even though I am slow, slow, slow. But, when I got up to 4-5 miles, my right hip/lumbar region started acting up. I would stop running for awhile, start again, and same thing. Finally, after many stops and starts, foam roller, stretching, I stopped in June, after running in a 5K race I promised my friend I would do (a charity race for the hospital she works for).
Well, last week, I realized that all of a sudden, my back isn't hurting! I mean, it hurt all of the time. Now, I am torn. I like running in the fall and winter; when I run and ride at the same time, at age 56 (almost 57), it seems to affect my cycling a lot. My legs are really heavy/sore. I do ride through early December, but by the end of october, it's less and less.
Yesterday, I did a 30 minute interval walk on the treadmill. I did lots of hill intervals at a 5% grade while walking, and i also snuck in 3 one minute running intervals at a very slow pace (5.6 mph). My back feels fine. But, I am still very uncertain if I should start up again. The fact that you can just go out the door and run, really appeals to me and it keeps the weight down, too.