Log message: Unable to load dynamic library timezonedb.so

Running Drupal 7 on a VPS with Hostgator on PHP 5.3. Installed Filecache module which increased performance for anonymous dramatically out of the box.

Then installed Authcache with Filecache as backend and followed these instructions for changes to my settings.php.

After completing installation of Authcache everything was fine according to status page, but performance was still slow for authenticated users and again slow(er) for anonymous users.

Enabled Authcache Debug module but the 'helpful little debug block' was nowhere to be seen. Adjustments on Debug config page or clearing cache did not help; no debug block.

Then enabled 'Log to watchdog' on Debug config page and noticed log messages:
"PHP Warning: PHP Startup: Unable to load dynamic library '/usr/local/lib/php/extensions/no-debug-non-zts-20090626/timezonedb.so' - /usr/local/lib/php/extensions/no-debug-non-zts-20090626/timezonedb.so…"

Followed these handy instructions to install timezonedb.so, and at the same time installed uploadprogress because my status page had been recommending that for a while now.

And then … BOOM, the rocket took off and the Debug block appeared! Still not sure why only Authcache module seems to need/notice the missing dynamic library, and if this actually is a bug because the very helpful log message pointed out what the problem was. Without that message I would have uninstalled the module by now.

Because I could hardly find any other posts about this issue with Drupal + Authcache install, I thought it would be useful to post here.

Thanks znerol and others for making my Drupal install perform like an authentic(ated) Rockstar!