WP Super Cache

Moved site to a VPS and now get this error message with WP Super Cache:
Warning! WP Super Cache caching broken! The script advanced-cache.php could not load wp-cache-phase1.php.

It says to edit advanced-cache.php with the absolute path to the plugin. I've done that, using the path supplied in the error message and double-checking with phpinfo.

I've also deactivated, activated and uninstalled the plugin and re-edited all the files that need editing. I defined WPCACHEHOME with the absolute path in wp-cache-config.php.

Nothing is working! Any ideas?