some times it happens...:
$ ./OPatch/opatch lsinv
Invoking OPatch 10.2.0.4.3
Oracle Interim Patch Installer version 10.2.0.4.3
Copyright (c) 2007, Oracle Corporation. All rights reserved.
Oracle Home : /export/home/oracle/oracle/product/10.2.0/db
Central Inventory : /u01/oracle/oraInventory
from : /var/opt/oracle/oraInst.loc
OPatch version : 10.2.0.4.3
OUI version : 10.2.0.4.0
OUI location : /export/home/oracle/oracle/product/10.2.0/db/oui
Log file location : /export/home/oracle/oracle/product/10.2.0/db/cfgtoollogs/opatch/opatch2011-02-02_14-30-01PM.log
List of Homes on this system:
Home name= OraDb10g_home2, Location= "/d03/oracle/product/10.2.0/Db1"
Inventory load failed... OPatch cannot load inventory for the given Oracle Home.
Possible causes are:
Oracle Home dir. path does not exist in Central Inventory
Oracle Home is a symbolic link
Oracle Home inventory is corrupted
LsInventorySession failed: OracleHomeInventory gets null oracleHomeInfo
OPatch failed with error code 73
Solution: