I am having a problem that's very similar to the one described here, except that the solution that worked for him (text encoding) didn't work for me.
I even tried applying
unix2dos -o style.css from the command line (which definitely changed the file from LF to CRLF, as I could see that the file increased slightly in size), but that didn't help.
I also tried clicking the button
Search Installed Themes but that didn't help either.
What are the requirements for making a child theme appear in the admin's list of Available Themes?