single.php not not found by The Loop

There is a “single.php” in my theme directory, but if I link to a single post (eg. http://www.aboutthecomposer.com/blog-test/blog/archives/147/) I get a blank page with “Archives” as the title.

My understanding is that, in the case of a specific post, WP looks for “single.php”, and uses “index.php” if it’s not found. I’ve tested for both single and index, and this blank page isn’t coming from either template.

You may notice that this is buried in a test subdirectory, so I wonder if that’s causing it to blow up.

Now, if I enter the URL as ……/?p=138, the single post does show up as desired, which leads me to think it’s a permalink-related problem.

Up at the root, on my live site, you can see the desired behavior: http://www.aboutthecomposer.com/archives/147/

Thanks a lot,
Michael