PHP’s open_basedir value giving a binary value in Apache logs

Reviewing logfiles to figure out why my site was down a few days ago, I found hundreds of lines like these (partially redacted with "x"):

[Fri Nov 27 23:14:36 2009] [error] [client xxx.xxx.xxx.xxx] PHP Warning: require_once(): open_basedir restriction in effect. File(/var/www/xxx/xxx.php) is not within the allowed path(s): (\xa0\x99\xc4) in /var/www/xxx/index.开发者_如何学Gophp on line 17

Note that the open_basedir value is binary, so it won't match anything.

No (admin) change was made on the server to cause this, and none was made to stop it.. it apparently resolved itself on its own (apache or other services weren't restarted/reloaded). The open_basedir directive in the apache conf file looks like this:

php_admin_value open_basedir /var/www:/usr/share/php

What would cause the open_basedir value to reload with a binary value, or where can I even start to troubleshoot this? This is the second time in the last two weeks this problem has arisen.

Apache version: 2.2.8, PHP: 5.3.0, Linux 2.6.24-23

Looks similar to this bug, which should be fixed in 5.3.1.