Segmentation fault on certain WordPress pages on Ubuntu / Apache / PHP

I’m getting reproducible errors when trying to access certain parts of a WordPress instance. This identical behavior occurs on two WordPress instances hosted on the same box.

The two actions that fail (and lead to an error page in Chrome (Error code: ERR_EMPTY_RESPONSE), and an error logged on server) are:

• Attempting to access the “General” settings page (/wp-admin/options-general.php)
• Attempting to confirm the deletion of any plugin

Apache2 error.log:

[core:notice] [pid 9173] AH00052: child pid 9181 exit signal Segmentation fault (11)```

Server Info:
```Ubuntu 14.04.1 LTS (GNU/Linux 3.13.0-24-generic x86_64)```

```PHP 5.5.9-1ubuntu4.5 (cli) (built: Oct 29 2014 11:59:10)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
    with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies
    with Xdebug v2.2.3, Copyright (c) 2002-2013, by Derick Rethans```

Please let me know what other information may be helpful. Thanks in advance.