As you're probably aware, the Jade (Crassula portulacea) isn't appreciated by the purists of the Bonsai world. However, the other 75% of us think it's probably one of the most attractive plants to bonsai.
The Jade, being a native of the drier African climates, absolutely does not tolerate over-watering. When you do water, flood the bonsai bowl, but then let the plant thoroughly dry out... perhaps as much as a month. The leaves should start to shrivel slightly before re-watering. If you had the plant in a shady area of the house and suddenly moved it to a more sunny clime it can be easily sunburned and perhaps that's what your seeing. However, since the Jade is reasonably care-free, I would excpect watering to be your culprit. Only a little 10-20-20 fertilizer and rarely at that (half strength).
Most people I know that cultivate Jade, re-pot the plant a lot more often than say, the junipers. Probably at least every 2 years and some do it every year, depending on how much minaturization they desire.
At any rate, ease up on the watering and do check closely for mealy bugs... but, thankfully they are rare... Best of luck, or, better yet, Nana korobi, ya oki!