I created a materialized view with the DI_TEST_AL user, let's name it MY_MVIEW. It appears in the USER_OBJECTS table as MATERIALIZED VIEW, I try to drop it, I get a success message, but the object is still there. In fact if I try to re-create it I get an error like "object already exists".
I see that there is a table with the same name belonging to another schema. I assume that should not cause the problem, but I felt like mentioning it.
Here is the SQL*Plus output:
SQL*Plus: Release 11.2.0.1.0 Production on Mon Aug 1 17:01:50 2011
SQL> select object_name, object_type, owner from all_objects where object_name = 'MY_MVIEW';
OBJECT_NAME OBJECT_TYPE OWNER
----------- ----------------- ----------
MY_MVIEW MATERIALIZED VIEW DI_TEST_AL
MY_MVIEW TABLE DIDEV11
SQL> DROP MATERIALIZED VIEW MY_MVIEW;
Materialized view dropped.
SQL> select object_name, object_type, owner from all_objects where object_name = 'MY_MVIEW';
OBJECT_NAME OBJECT_TYPE OWNER
----------- ----------------- ----------
MY_MVIEW MATERIALIZED VIEW DI_TEST_AL
MY_MVIEW TABLE DIDEV11
SQL>
I double checked my permission and DROP ALL MATERIALIZED VIEWS is granted to the DI_TEST_AL user.

DO_OPP_SEARCH_MVIEW? – Jack Douglas♦ Aug 1 '11 at 16:45STATUSin the select onALL_OBJECTS. I have also this problem, and for me, status on the materialized view isINVALID. – awe Apr 17 at 6:29