So far, StuffIt hasn't done it. I suppose this is a lost cause.
Thanks for all your help.

The file is one of over 1600, created by a file-recovery app. I've considered the possibility of file corruption; I just want to be able to look inside a few of the .gz archives to be certain of their contents before I trash the lot of them.

Well, nuts. I was afraid of that.
Can anyone recommend another mean to decompress .gz archives? Archive Utility and Stuffit Expander don't work. I've gingerly tried various Unix utilities in Terminal, but get the same results each time:

invalid compressed data -- Huffman code > 32 bits packed data

Being barely a Unix non-virgin, I'm in dire need of help with mac-gzip-111-src.hqx. I've read much of the documentation, but find myself at a near-total loss as to what to do.
Can I even use the utility on an Intel Mac?

Technicalia: iMac, 2.8 Ghz Intel Core Duo, 10.5.8, 2 GB MHz DDR2 SDRAM.

I will ...