Database error

[GoHorns123]

Can anyone tell me why I would get this database error for a couple of hours, and then the board went back to being fine & running. What would cause this error?

Invalid SQL:

SELECT *
FROM datastore
WHERE title IN ('','options','bitfields','attachmentcache','forum cache','usergroupcac
he','stylecache','languagecache','products','plugi nlist','cron','pr
ofilefield','userstats','birthdaycache','maxlogged in','iconcache','eventcac
he','mailqueue');

MySQL Error : User 'i' has exceeded the 'max_questions' resource (current value: 50000)
Error Number : 1226