One of my users is getting this (I have replaced the actual package with the string 'NAMEOFPACKAGE', and the name of the database with 'THEDB'):

Error (-4068)--(ORA-04068: existing state of packages has been discarded
ORA-04061: existing state of package body "THEDB.NAMEOFPACKAGE" has been invalidated
ORA-04065: not executed, altered or dropped package body "THEDB.NAMEOFPACKAGE"
ORA-06508: PL/SQL: could not find program unit being called

Can someone recommend the best way for me to trouble shoot this and figure out what the cause of the problem is? They said they tried to run the application that is generating this error several times.
The 'NAMEOFPACKAGE' is one we have written, and seems to work fine in other databases.

Jeff Kish