I'm having a weird one.
For the longest time, I've used WP SuperCache with success.
I have two blog installs. One at macnightowl.com, and another at macnightowl.com/newsletter. Both installations are near-identical, except for minor configuration changes in the theme file to reflect the different locations of the blog files.
With the installation of WP 2.5 in both folders, your plugin stopped delivering information about the file being cached, although cache files are being created in the macnightowl.com installation.
<!-- 26 queries. 0.617 seconds. -->
<!-- Dynamic Page Served (once) in 0.614 seconds -->
For macnightowl.com/newsletter, zero cached files, nothing in the Cache folder. Write privileges and installations are identical, and the .htaccess files of both represent the different locations of the installations.
Can you suggest a solution for someone who isn't an expert at PHP stuff? Or something to look for?