what ISO did you have it set at?

If you are indoors with no flash it is probably better to use a high ISO, even with the aperature wide open.

What aperature did you have it mainly on? Was it always about 1.8 or smaller? I don't think wide open would be too good though, as it wouldn't give you a good dof and is harder to get an area which you want to be sharp (eyes especially as it could be only the ears or the nose in focus if the focus is not spot on). With people moving around I think it would be harder too with a wide aperature. The blur with the smaller aperature (higher number) can be corrected by using a higher ISO (which would make the speed faster). I have learnt that to take photos whilst hand holding your camera, use the same (or a bit faster with crop sensor cameras) number as the lens. You used a 50mm, so your speed should be approx. 1/60 or more to safely hand hold. Works for me.

Don't forget, even pro's have duds! Maybe others who have done Weddings or Events can help out better than I.