mysql duplicate entry error when there is no duplicate entry (bulk load via php)

> repair table mytablename;

> truncate table temptable;
> truncate table importtable;

> #bulk insert new data
> insert into importtable(col1,col2,col3)
> values(1,2,3),(4,5,6),(7,8,9);

> #now archive the live data
> insert into temptable(col1,col2,col3)
> select col1,col2,col3 from livetable;

> #finally copy the new data to live
> truncate table livetable;
> insert into livetable(col1,col2,col3)
> select col1,col2,col3 from importtable;