I would say that the 1/10 sec shutter speed is your problem. Shooting at that slow of shutter speed it is very difficult to keep the camera from moving and blurring the picture. Also if you are shooting at F1.8 and shooting this close and were shooting with a tripod you would only get a few stings in focus due to the very small depth of field.
I agree with you on this Jeff. But, when you're caught you can do better with two different things.
1st, you can use the mirror up setting. You focus, click (the mirror goes up), steady yourself and then press the shutter to take the shot. This takes the mirror movement out of the equation.
2nd, you can use the "Quiet" mode. This slows down the mirror and gives you a little more sharpness at slow shutter speeds.
But there is a limit and sometimes you'll have to take a few shots to get one sharp. Make sure you review at 60% or larger on the camera's lcd.