In DB Navigator, user unable to view the partition ranges of a partitioned table that owned by another user.
Use DBA_VIEWS instead of ALL_VIEWS
Steps to enable the DBA_VIEWS:
1. Check Enable DBA views in Preferences
2. Grant user the following privileges: SELECT ANY TABLE privilege, DBA or SELECT_CATALOG_ROLE role. The latter is the most frequently preferred as it is less powerful.
This issue is fixed in SQL Nav 4.1.2. You can download it at http://www.quest.com/solutions/download.asp