As a previous poster mentioned, if it's a mid to late "E"-series production frame, Glock Inc. SHOULD replace it for you. The issue is with "E"-series Glocks (all size frames and models, regardless of caliber) manufactured from around "EJx xxx" or "EKx xxx" thru around "FAA xxx" or so. It was over eight or nine months or so of production but it didn't effect ALL Glocks during that time-frame. Most seem to have been fine, others break the left (or right) rear frame-rail from use. The time period of production was from around July 2001 to around May of 2002 or so.
The only reason I mention the "F'-series serial-number at all is that there was speculation that the affected rear-frame rails might have been used into the very early "F" serial-number range until Glock diagnosed the issue. Glock, Inc. added a "1" to the serial-number of the replacement frame(s), when they were Factory replaced under this "recall". Good luck.