This is most likely a bug caused by an old eAccelerator version. eAccelerator is script that can be installed on servers to optimize PHP execution. However, only the most recent versions are fully compatible with PHP 5, so if you are having issues, install the latest release or disable it completely.

http://eaccelerator.net/wiki/Release-0.9.5.2

If you are on a shared hosting server, ask your host to do the update.