Three-Way Switch Tripping Circuit

[target]

I think this may be an issue somewhere with the main circuit box (which I have not looked at).

Here is the setup:

Three-wire line (ground, negative, 2 hot) running up to second level of house, on two separate circuits. One line runs through a receptacle and to the first 3-way switch (the receptacle wiring is correct, based on a plug-in analyzer). The wiring from the first 3-way switch runs to a light, and then to the second 3-way switch. I have reviewed the wiring numerous times, and am confident it is correct (hot in to common, neutral in to light, travelers connected between switches, and common from second switch to hot on light).

When I switch on power, the light works fine from the second switch (on-off no problem). However, when I go to the first switch, the circuit immediately trips (both with light on and off). If I leave the switch as-is after tripping, I cannot reset the circuit. If I move the switch back, the circuit will reset.

I have no idea why this won't work. I would imagine that if something were wrong at the main circuit box, it would show up at the first receptacle. However, that appears to have proper hot/neutral/ground.

The light does work if I replace the first switch with a regular switch and forego the second switch.

I also did try a second three-way switch, to rule out a possible bad switch.

Any suggestions will be greatly appreciated!

[kactuskid]

What did you change for this to just start happening, is this a new circuit or one that previously worked? It sounds like you have a direct short to ground from your 1st switch. That's why it trips each time you put it in the on position. The white wire going to the second switch from your ceiling fixture must be remarked as a hot wire. The other end of the white is attached to the black in the ceiling box. Here is a link to give you a diagram of how it should be wired. Look at the second picture on the link. Hope this helps.

http://www.wfu.edu/~matthews/courses/p230/switches/3way/variations.html

[target]

I have the wiring between the second switch and the light correct (white marked as hot, etc.).

To clarify, this light was previously switched from a single switch, at the top of the stairs. The previous owner had run wiring down to a box at the bottom of the stairs. I tried to hook it up, and also had the same tripping issues (which is probably why the previous owner only used one switch). I am working on an upper level remodel, and thus thought I might as well get the three-way switches working for this light, but am now having issues.