Weird Wiring Problem

Some years ago, I installed two automatic timer switches next to each other. They have built-in digital timers to automatically shut off the two outside lights. They work great, although every four or five years, I have to replace them, because something in the switch breaks. They're not expensive, and it's no big deal.
Last Summer, I replaced them with two somewhat more expensive switches which I bought at the electrical supply store. As usual, they worked fine. Until recently. One of the switches just stopped working. There was no digital display, no nothing. I assumed it was a bad switch that had died prematurely. This afternoon, I removed it and was about to head down to the electrical supply store to replace it, and I thought, just to be sure, let me check the wiring, to make sure that's not the problem.
Here's what I have:
Two separate sets of wires come of the box. The switch that stopped working was wired the same as I've had them both wired for years: The black and white go to the two wires on the switch. The switch next to it, (the one that's functioning), is wired to it's two wires, black and white, exactly the same.
When I take my light bulb/circuit tester, here's what I find:
When I connect the two wires that were connected to the non-functioning switch, nothing happens. When I connect the two wires connected to the functioning switch, the bulb on the tester lights, (as I expected).
Now, back to the wires from the NON-functioning switch: When I connect the hot wire to one end of the tester, and touch the other lead to the box, it lights. When I connect the hot wire from the non-functioning switch to the ground on the other switch, it lights. When I connect the hot wire to from the functioning switch to the ground on the non-functioning switch, it does NOT light.
My conclusion is that something has changed with the ground side of the wiring that was connected to the non-functioning switch.
These wires have been in place for years, since before I bought my house. They've never been moved or touched. All of a sudden, I'm seeing this change.
I checked the breaker panel, and of course, the connection there seems to be fine.
Any helpful input or thoughts are definitely needed here.
Thanks in advance!
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If I had to hazard a guess based upon what you are telling me, I'd say the bulb that the "non functioning" timer is controlling is burned out. Two wire electronic time switches require a trickle of current to flow through the lamp or lamps that they control to function. If you put your bulb tester across the two wires that the switch was connected to and got no light, you've either got an open circuit or a blown bulb. I'm guessing the bulb

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You're right. I thought it had to be something simple, but I guess I spent so much time staring at it, I lost the forest through the trees. You have my gratitude.
I guess I'll cancel the electrican.
On Sat, 15 Apr 2006 16:11:21 -0400, "RBM" <rbm2(remove

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What you say is funny, we all seem to have a tendency to do it

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