Have you set any of the design-time preferences in the IDE (Oracle Menu, Preference item)? If you have set the OralceHome or OCIDLL values, clear them, restart Delphi, and try again.
If this does not apply, verify if you have set the OracleHome or OCIDLL variables at run-time in your application. If you have, set the design-time preferences accordingly.
I hope this helps.
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Marco Kalter
Allround Automations