I wouldn't worry either - you're just turning fat into muscle, which weighs more. With weight training you should quickly start seeing results in terms of more defined and shapely muscles.

One thing I have always been frustrated by is that when I was riding a lot I found I ate a lot more, which seemed to offset any weight loss from the exercise. I often let lots of exercise fool me into thinking I can eat whatever I want. Unfortunately, I've come to the realization no matter how much I exercise I still can't live on chocolate.