ORA-00604 ORA-04031 while issuing a DROP USER USER_NAME CASCADE statement

Hello,

I received this error message when I issue the drop statement. We are using a 9.2.0.3 DB on UNIX OS. I have been able to drop other users within the same session, but this particular user is causing problems.  I flushed the shared pool, but I still received the same error message. Thank you in advance for your assistance.

drop user DW_031000 cascade
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1 ORA-04031: unable to allocate 4160 bytes of shared memory ("shared pool","unknown object","sga heap(1,0)","state objects")

shared_pool_size 20971520

Total System Global Area 53216888 bytes

Fixed Size                   730744 bytes
Variable Size              50331648 bytes
Database Buffers             819200 bytes
Redo Buffers                1335296 bytes