I broke down and bought a digital scale yesterday (cheapy $20) and it doesn't seem to work.

I press the corner and it blinks and zeroes out and then I put weight on it and it does nothing at all (just blackness), or the E comes up. I haven't wanted to stand on it yet, because I'm not due to weigh in for four more days. It is supposed to weigh accurately from .2 lbs to 300 lbs, and I've put heavy jugs of water on it and zilch. Anyone else had trouble with a digital scale? Is it something I'm doing wrong? Have you ever tried weighing anything besides yourself on it?
The last time I looked at buying a digital scale I talked myself out of it, because in the store I put some weights on them (from the workout section) and each one I tested showed a couple of lbs more than the weights I put on them. I figured if it was off a couple of lbs for 25lbs of weights, it might be off even more for my weight. I didn't need that kind of discouragement.
I can barely read my dial scale any more, so I figured I'd live with the numbers, even if they aren't accurate, as long as they still reflect me losing. So, have any of you tested your digital scales to see if they actually weigh true?