There was a type casting problem in the storage/innobase/handler/ha_innodb.cc,
(int ha_innobase::write_row(...)). Innobase uses has an internal error variable
of type 'ulint' while mysql uses an 'int'. 
      
To fix the problem the function manipulates an error variable of
type 'ulint' and only casts it into 'int' when needs to return the value.