from 8.0.5 to 8i

hi
i have developped an application with designer 6 an 8.0.5 .
it run fine if i export my database to another 8.0.5 database my appli run fine also but if i migrate to 8.1.5 my appli don't run some queries correctely.
Afterward my appli is disconnected from the database.
why please :o

Don't know why without knowing what the query is.

The query is only a select one.
It is a query to populate a block.