help!! after edited the display string in invite.module

I need to edit some display string in invite.module, such as the hints of invite form

after edited some of them, i got

user warning: Unknown column 'i.mid' in 'field list' query: SELECT i.mid, i.email FROM invite i INNER JOIN users u ON u.uid = i.mid AND u.status = 1 WHERE i.uid = 4 AND i.timestamp != 0 AND i.received = 0 in /home/happy84/public_html/shangxiapu/includes/database.mysql.inc on line 174.

The worst problem is, when i restore the original invite.module from 5.x 3.0, restore the db, the error msg still exists, how to take me back to the start?

Any one help?

BTW, how to edit these display strings fluently, except the solution of translating them in locale module?

Thanks