CONDITIONS PREFERRED:
The jade plant loves bright indirect light, although it will grow in partial shade. The soil should be very well drained (I recommend 1" - 2" of horticultural charcoal in the bottom of the pot, then a commercial
cactus and
succulent soil mixture or 2 parts common houseplant soil mixed with one part sand). The jade plant does better when rootbound (repot a well established plant every 2 years). The plant prefers to keep its feet dry, so let the soil dry out between waterings. The best method for watering is to fill your sink up with water and soak the plant until air bubbles stop rising from the soil, then let it drain completely. Avoid getting water on the leaves (if the leaves get wet during watering, do not immediately place it back in sunlight, the water will act as a magnifying glass and cause burns on the leaves). It must be stressed -- let the soil dry completely before watering (this is the "thrive on neglect" part).
Are you watering too much?
Have you re-potted lately?