I’m getting this too. White screen of death (500 error) when basic disk page caching enabled (disk database and object caching works fine).
Log says:
PHP Fatal error: require_once() [<a href='function.require'>function.require</a>]: Failed opening required '/PATHNAME/wp-content/db.php' (include_path='.:/usr/share/pear:/usr/share/php') in /PATHNAME/wp-includes/load.php on line 331
in my case i do not see any 500 error.. just a blank page.. where is supposed to see the page content..
pr0t0c0l: What does your php error log say?
[21-May-2013 09:41:45 America/New_York] PHP Fatal error: PHP Startup: apc_mmap: mmap failed: in Unknown on line 0
[21-May-2013 18:26:04 UTC] PHP Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0
any way i have changed to the old version.. 0.9.2.10 everything is working just fine again..