Have you tried the wp_cache_clear_cache() command? You could also enable debugging in the plugin. That should tell you a lot.
Yes, I ran wp_cache_clear_cache(), no luck.
And thanks for the tip about turning on debugging. I’m seeing some interesting lines in my log:
09:09:49 [fname] Cookie detected: wordpress_logged_in_bb5263af5c15c9efc60dc461c01624d5
09:09:49 [fname] supercache dir: /home/johnhell/radiovalencia.fm/wp-content/cache/supercache/radiovalencia.fm/override/unscheduled_show_processor.php/
09:09:49 [fname] No wp-cache file exists. Must generate a new one.
09:09:50 [fname] Cookie detected: wordpress_logged_in_bb5263af5c15c9efc60dc461c01624d5
09:09:50 [fname] In WP Cache Phase 2
09:09:50 [fname] Setting up WordPress actions
09:09:50 [fname] Supercache caching disabled. Only using wp-cache. Non empty GET request.
09:09:50 [fname] Created output buffer
09:09:50 [fname] Output buffer callback
09:09:50 [fname] No closing html tag. Not caching.
09:09:50 [fname] wp_cache_shutdown_callback: collecting meta data.
What really has me curious is this one:
09:09:50 [fname] Supercache caching disabled. Only using wp-cache. Non empty GET request.
Does that mean I’m not using the WP Super Cache plugin for caching?
Probably some plugin is populating the $_GET array on every request. Unfortunately you’ll have to disable each plugin or search through your plugins one by one to find the offending one.
Are you still using wp-super-cache? Give the development version a go (download here) as I changed a restriction on clearing the cache that may have caused this problem.