Oracle error occourred, but error message could not be retrieved from Oracle

This is the error I get while trying to connect to Oracle using ADO...
It started after I reinstalled the machine. Everything was going perfectly
before.

The connection string is the following:

Provider=MSDAORA.1;Password=x;User ID=myuser;Data Source=SRVOHLPROD;Persist
Security Info=True

I am running Windows 2000 and Personal Oracle 8i is installed. I am trying
to access an Oracle 8 db or the local one, but it gives me the same
problems...

I drop a TADOConnection on the form and I set these parameters but when I
try to set Connected to true the first time gives me the error. After that
it works ok.
If, insetad, I create the TADOConnection by code it always refuses to
connect.

Any idea?