This sounds like a configuration problem of the database (schema), although I'm not quite sure why this would have changed from the default.
Can you run the following query on your database?
describe mdl_scheduler id;The expected output is:
# Field, Type, Null, Key, Default, Extra
'id', 'bigint(10)', 'NO', 'PRI', NULL, 'auto_increment'The "auto_increment" bit is what I suspect might be different in your DB.