Okay, when I first moved into the house, everything worked fine. After about a year, my garbage disposal stopped working. I thought maybe it was jammed but the blades still move when I turn the hex on the bottom. I just noticed tonight that if I reset this one outlet, and turn on the disposal switch, it trips the outlet. I tested this serveral times this evening. The disposal is plugged into another outlet under the sink, the outlet that trips is a different outlet. Any thoughts on what is going on and how this can be fixed??
The receptacle that the disposal is plugged into is fed from the Load side of the GFCI receptacle, thereby providing ground fault protection to the receptacle. There is a ground fault somewhere between the GFCI and the disposal, which is causing the GFCI to do it's job and trip.
You'll have to locate the fault, and fix it. If you don't have (or know how to use) a multimeter, you'll want to contact an Electrician. If you have a multimeter and know how to use it, you can narrow down where the fault is by checking continuity between hot and ground.
Start by turning off the breaker, and insuring power is off in the area you'll be working. Unplug the disposal and do a continuity test between the hot blade (smaller blade) on the plug, and the ground pin (long roundish pin). If the test shows there is not fault in the disposal, move up the circuit to the next device (receptacle) and test again (don't plug the disposal back in). If you still haven't found the fault, continue working your way up the circuit (the switch next) until you reach the GFCI. If you still haven't found the fault, try replacing the GFCI receptacle (making sure to hook it back up the same way).
If you still cannot resolve the issue, it's probably best to call in an Electrician (since they'll have cooler gadgets to troubleshoot the circuit). I would focus most of my attention on the disposal and the switch, since those tend to be the usual culprits.
Your garbage disposal is wired through your GFCI outlet. This is generally not required by code*, and in fact motor based appliances can cause GFCI breakers to trip. This is why even though your washing machine is in a wet environment you don't use a GFCI for it - it may trip even when there's no ground fault condition due to the motor.
Generally as motors age they become more electrically noisy due to poor electrical contacts on the carbon brushes and contaminants on the brush contacts. This doesn't necessarily mean that continuing to use the garbage disposal is unsafe.
Further, even GFCI breakers age. It's quite possible that the garbage disposal hasn't changed at all, but the breaker has become more sensitive over time.
At any rate, you have a few steps for resolving this issue:
* Please check with an electrician familiar with your local code requirements