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.
There was a file locked by cache store system.
1.Execute script purgecaches to reset the cache system.
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 .