Unexpected database error


I am trying to set up a MySQL database with WebTrees. I get an unexpected database error. Why does MySQL do this?

Setup wizard for webtrees

An unexpected database error occured.

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (cwilson_2012_09_15.wt_block, CONSTRAINT wt_block_ibfk_3 FOREIGN KEY (module_name) REFERENCES wt_module (module_name))
The webtrees developers would be very interested to learn about this error. If you contact them, they will help you resolve the problem.

– Alan Wilson