Sure can be.

When you bought the bike, did the LBS at least do a basic fitting for you? A good saddle position depends a lot on how far forward or back in relation to the pedals.

http://ts3.mm.bing.net/th?id=H.46317...h=177&c=7&rs=1

This is a simple drawing of the "KOPS" principle (Knee Over Pedal Spindle); basically, it's a measurement that puts your leg at the proper angles to produce smooth power without excess effort. The drawing calls for that line down from the knee to SPLIT the pedal axle; personally, I like it about 15-20mm behind it. More than that, and I feel like I'm pedaling through deep sand; less, and I feel like half my leg muscles are getting left out.

Some people swear BY 'KOPS'; some people swear AT it. But get checked, so you know if you're close or not, and can GET close.

Also, moving the saddle a full inch all at once can cause that, since it changes how your muscles work in the pedaling motion; too much change=pain.