I went into the WP-Supercache settings, and it gave me a warning that the wp-content directory was writeable, so I changed it to read-only. Then it said that certain things need to be writeable for WP-Supercache to work, so I changed those back to writeable. Then I hit the "Test" button to check that WP-Supercache is still working. The "Test" button had always worked before. But now, it takes awhile and then gives a 500 internal server error. Worse, when that happens and I go to the site in another browser, the logo image is broken and search doesn't work. To fix that, I have to hit "delete cache," and then the site works again. I figured that to fix this, I would make everything in the site writeable. So I did that; everything is just as before...all writeable. But the "Test" button still gives the 500 internal server error and breaks the pages, causing me to have to "delete cache" to get the site working again. So basically the fact that I changed the permissions once seems to have broken WP-Supercache, and changing them back to the way they were before doesn't seem to help.
Unfortunately, I cannot see a PHP error log because this is economy hosting on Windows. But obviously this is some sort of bug with WP-Supercache that's causing this, and my description above ought to help pinpoint the source of the problem. Any help would be appreciated.
Thanks!