My client's 1.5.0 site (which was upgraded from 1.3.8a with the official upgrade procedure several months ago) has just discovered that the gift certificate function no longer works. This is the first time someone has tried to buy one since the upgrade. I tested it myself, and the purchase process seems normal. But when I logged into the admin, there was no certificate in the queue to release for redemption. The product is set up properly (as all along - since it functioned fine for years in the 1.3.8a version of this same site).

I am thinking maybe a fresh upload of the gift certificate function files might take care of this - assuming a file has been corrupted. But I have no idea what files to upload.

This site has the following modules:
USPS
Image Handler 4
Zen Lightbox (install *after* IH4)
ZX Slideshow

The host is GeekHost, running PHP Version 5.3.19.