Disregard this if you have already addressed dbcc upgrade_object output.
One of the steps to run after upgrade for a user database is
dbcc upgrade_object (database [,object_type])
This usually will complain about missing objects needed for recompilation.
Other than that,
when you get stack traces then SAP/Sybase TS is the way to go as Jean-Pierre as mentioned !
HTH
Avinash