Apache stopped responding to requests after APC cache flush

Hi everyone, My busy Apache 2.2.8-1ubuntu0.14 server running PHP 5.2.4-2ubuntu5.7 using APC-3.0.19 stopped responding today and did not accept connections for a couple of hours - I had to stop and restart it manually. Apache's error log looked like: (Trivial error messages every 10 seconds or so, such as:) [Sat Dec 19 14:36:37 2009] [error] [client 74.215.40.13] File does not exist: /vol/public_html/vol, referer: http://www.chickensmoothie.com/ (and then...) [Sat Dec 19 14:36:39 2009] [apc-warning] GC cache entry '/vol/public_html/help/index.php' (dev=2160 ino=953674) was on gc-list for 3603 seconds [Sat Dec 19 14:36:39 2009] [apc-warning] GC cache entry '/vol/public_html/Forum/style.php' (dev=2160 ino=951667) was on gc-list for 3603 seconds [Sat Dec 19 14:36:39 2009] [apc-warning] GC cache entry '/vol/public_html/Forum/search.php' (dev=2160 ino=951664) was on gc-list for 3603 seconds (and so on, about 20 or 30 more entries like that, and then...) [Sat Dec 19 14:36:39 2009] [apc-error] apc_sma_free: could not locate address 0xdd0a48 [Sat Dec 19 14:36:44 2009] [error] [client 94.112.36.156] File does not exist: /vol/public_html/fanp, referer: http://gaara-a-gaarinka.pise.cz/garinka/012009/ [Sat Dec 19 14:36:56 2009] [error] [client 82.246.148.148] File does not exist: /vol/public_html/Forum/favicon.ico [Sat Dec 19 14:37:00 2009] [error] server reached MaxClients setting, consider raising the MaxClients setting (then nothing in the log for 2 hours. I think all the Apache clients were sitting there hanged up to the MaxClients limit. Then I manually stop the server...) [Sat Dec 19 16:20:00 2009] [notice] caught SIGWINCH, shutting down gracefully [Sat Dec 19 16:20:01 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.9 with Suhosin-Patch configured -- resuming normal operations Does "apc_sma_free: could not locate address 0xdd0a48" indicate a fault in APC, or does this message frequently appear in normal operation? The timing suggests to me that APC caused the hang. Cheers, Nicholas Sherlock