When running wpdb->insert the result returns false. All the values seem to check out to be fine.
The problem might be due to this bug in WordPress. Basically one of your fields is too long and WordPress is not completing the insert. Reading through the ticket, it seems it is a WordPress error and not a MySql error so it would be pretty difficult to go through all the fields, determine the column field size limits, and then return an error of some sort. Anyway, this is one possible reason to wpdb->insert returning false.