Nothing comes straight to mind, I'm sure others may have some suggestions for you. A few obvious things:
Clear the cache;
Check your database health;
Checked the logs
Switch on debug by IP incase it offers more tips;
Find out if anything on your host server has been changed recently. PHP versions etc? Post whatever more information you can find here.
www.dbinformatics.com.au
We are always interested in hearing from experienced eZ PHP programmers and eZ template designers interested in contract work.