Error in Moodle:

Coding error detected, it must be fixed by a programmer: Failed to unserialise data from file. Either failed to read, or failed to write.

Problem:
There was a file locked by cache store system.

Solutions:

1.Execute script purgecaches to reset the cache system.

php /moodle/admin/cli/purge_caches.php

2.Remove all files and directories unde directory /moodledata/cache

Finally, please don't edit core files to solve this problem. Think, in Moodle always was a alternative solutions. Find in Moodle tracker system .