daven1986,

You might be onto something with chain tension. To check, pick up or somehow support the rear wheel off the ground (I use one of those showroom bike holders that hold up the rear by the axles) and give the rear wheel a push. The chain will loosen and slack a bit because no crank or cog is truly round. What you want to see is if chain tension slows/stops the wheel from spinning. You'll probably have to spin the wheel a few times. If it does stop/inhibit free spinning loosen the chain up a pinch. Repeat until joy returns to your life.