500 Internal error -- Non-static method should not be called statically

I've had an installation of Gallery2 integrated w/ Drupal running for a number of years. Recently, I started getting 500 errors on the Gallery pages, and I'm pulling my hair out trying to get to the bottom of this.

So far, I've downloaded the latest Gallery 2.3.1 release and laid it over the top of the 2.3 install. I went through the upgrade scripts, which seemed to work fine. Still getting the 500 errors, though.

I'm on 1&1 (yes, I've heard all the whining about them, but this site's been up for years, and this is a non-profit, so they don't have a bunch of money to drop on a "good" host). Anyway, I can't get the apache log files, but I was able to dump error info to a file, and I'm seeing the following:

gallery2/modules/core/classes/Gallery.class: "() Non-static method GalleryDataCache::containsKey() should not be called statically, assuming $this from incompatible context"

I've tried setting error_reporting in a local php.ini file ("error_reporting = E_ALL & ~ (E_NOTICE | E_STRICT);"), and I believe this is being read, but it doesn't seem to be helping w/ the error at all.

php version: 5.2.17
Gallery url: http://troop734.org/gallery2/main.php
phpinfo url: http://troop734.org/gallery2/troop734info.php

If anyone could throw me a clue, I'd appreciate it. Although this would be a little more work than I'd hoped for, I'd consider an upgrade to Gallery3 if there's a working integration w/ Drupal (last time I checked, this wasn't yet in place).

Thanks in advance.