Hello,

This is a long time problem, it is caused by collisions when cache file is saved by more apache processes at once. Unfortunately, there is currently no reliable way to lock the cache file when writing in PHP. If you are using JoomSEF version 3.5.5, there should be only the "Cache file corrupted" message visible and the website should be running with no problems. There will be an option not to show the message either in some future version.

Best regards,
ARTIO Support Team