Unable to install patchset 8.1.7.4

Hi all,

I'm trying to upgrade a 8.1.7.2 db running on AIX 4.3.3 to version 8.1.7.4 (don't laugh ;-) ).
The problem is that the OUI doesn't "detect" the installed software and always gives me the message "there are no patches that need to be applied" ...
I already did some research :
- the environment params (ORACLE_HOME, ORACLE_BASE, ...) of the Oracle owner : OK
- /etc/oraInst.loc : OK
- the binary file OracleHomesList.ser under oraInventory/Contents : NOT OK
=> this doesn't hold a reference to the correct ORACLE_HOME folder !

I have no idea how the software was installed, but I have the impression that it was copied from another server ... So is there any way to add the correct ORACLE_HOME dir to the OracleHomesList.ser file ? I believe my only other option is to reinstall the Oracle software from scratch, but can I do this without having to restore my whole db ?

Thanks,
Matthias

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"We are all in the gutter, but some of us are looking at the stars"
Oscar Wilde