This may be the database server, or if it happens doing a specific action, the mail server (if you have configured email settings).
If it's the email server, check if you can connect to it from the server running Media Wiki, for example, running the Telnet client to the server and port configured on $wg SMTP and seeing if it can connect.
If you receive the error "Error occurred during initialization of VM, Could not reserve enough space for object heap, Could not create the Java virtual machine.", try increasing the value of $wg Max Shell Memory. For more information see the comments on PHP: imagecreatefromjpeg (function synopsis) Assuming you get this error even when you do have a seemingly valid logon session: If your Apache server has the Hardened PHP patch, you may need to edit several variables in your /etc/file if you wish to have wiki pages with large amounts of content.
On some Linux and BSD installations rsvg is renamed: Instead of setting (default) One cause: the number of pixels in the original image exceeding $wg Max Image Area. In particular, consider the settings for varfilter.max_value_length, max_value_length, and hphp.request.max_value_length.
By default, it is set to use Image Magick for conversion. Ensure that your $wg Image Magick Convert Command variable is valid.
Common settings are: If generating thumbnails with Image Magick fails with a web server error log message like "Memory allocation failed" or "/bin/ulimit4.sh: Segmentation fault /usr/bin/convert ...", the $wg Max Shell Memory value may need to be increased.
Many people report blank pages in recent versions after submitting articles to their new wiki. This change does not require you to restart apache.
When the path is missing non-ASCII characters When using IIS/Fast CGI on Windows, the guest account that is used also needs execute permission on %SYSTEMROOT%\System32\otherwise you'll receive an "Unable to Fork" error.
Media Wiki places time and memory limits on shell commands under Linux.