Oracle Discoverer is a GUI data browsing/query tool, and it's installation would change the libraries installed on the local ORACLE_HOME.
If your script has worked on this server before, Discoverer was recently installed, and now it does not work, I'm gonna put a better than 50% chance this is the problem. (Besides, there are a lot of "features" with the Oracle 8i OCI, and changing a lib or two can make things more "interesting". *Smiles*)
There is one additional problem -- the Oracle installer is horrid. I am not sure uninstalling Discoverer will remove everything which it added. (I am an Oracle DBA, and I cannot tell you how many times I have had to scrap my local install and start all over when adding new components.) If you have a recent backup which can be restored (including the reg keys under HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE) this is where I would start. If not, and you can take the machine down, I would uninstall the Oracle software, remove the ORACLE_HOME directory, remove ORACLE_HOME\bin from the PATH, and remove the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE reg keys. Then I would start from square one with a new Oracle client install.