Product review (1 stars): Buy them in bulk; they keep breaking!
The one that came with the fridge broke in about six months. This one broke in three months. As others have said, the weak points are the tabs at either end.  It's a terrible design or it needs to be made from a more durable material. So, I can resign myself to buying 2 or 3 every year or take up the issue with Sears.  I'll see if I have any luck with the latter and will repost with the outcome.

Follow up -- So, I called Sears to complain.  The first person to whom I spoke suggested I was putting too much weight in the drawers. I assured her I was not putting bricks in them, only the fruits and vegetables for which I believe they are designed. She was sympathetic but could not offer any satisfaction. She referred me to a number I could call to inquire if there are any recalls for this issue. That department assured me there are not.  Finally, after a few more calls I reached the department where I could lodge a complaint.  I was given a case number and told I would be contacted.  That was just 3 days ago; I've not yet heard back.

So when the new rail arrived (my third one), I decided to take matters into my own hands and try to correct a lousy design.  I took a metal T-strap available at any home center and cut it into two pieces. Using PC 7 epoxy I attached it over either end of the rail. The T-strap has screw holes in it. Let the epoxy ooze through the holes and spread it out to help with adhesion.  See photo. There is just enough room in the slots from which the rail hangs that the glass shelf that sits on top still lies flush.  Anything thicker than what I used or too much epoxy would interfere.  We'll see how it works out.

In the meantime I would encourage everyone experiencing this problem to call the manufacturer of their fridge (this rail is used in a number of different ones) and register a complaint. If they hear from enough people they may acknowledge that this part is inadequate for its intended purpose.