An example of the error reported after SHUTDOWN IMMEDIATE:
SQL*Plus: Release 10.2.0.3.0 - Production on Sob Jan 26 14:23:59 2008 Copyright (c) 1982, 2006, Oracle. All Rights Reserved. Connected. Database closed. Database dismounted. ORA-00600: internal error code, arguments: [LibraryCacheNotEmptyOnClose], , , , , , ,  Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production With the Partitioning, OLAP and Data Mining options
According to Metalink note 4483084.8 “Bug 4483084 – OERI[LibraryCacheNotEmptyOnClose] on shutdown” this error message could be ignored. Bug is fixed in 188.8.131.52.
We’re getting this error sporadically after we migrated to 64-bit 10g R2, never received the error before (on 32-bit OS/RDBMS).