Did you move the scale after you calibrated it? You need to recalibrate anytime you move a scale whether its a beam or electronic scale.
I use an RCBS (Ohaus) beam scale but would like to move up to an electronic scale to save a bit of time. I have utmost faith in elctronic scales- I use them alot where I work- if they are mounted to a granite table, they pretty much never go out of calibration- even our ultraprecise balances that weigh out to the 100,000th of a gram though these babies cost $15,000 a piece not $150.[8D]