My present setup is Windows Vista Business, Toad Version 22.214.171.124
My Windows Vista system had Oracle 8.1.7 client and Oracle Developer 6i installed. Once the server database was upgraded to Oracle 10g R2, new version of Toad 126.96.36.199 was installed and was able to connect using Oracle 8.1.7 client network.
As the client and server version was different so installed the latest Oracle client version 10.2.0.1.0 and configured Toad to connect the server Oracle 10g database. Till this point the connection with Toad was smooth and working.
In order to develop the application, latest Oracle Developer suite version 10.1.0.4.0 was installed and was able to develop application.
Later when I tried connecting server Oracle 10g Database through Toad the above error surfaced. I searched on the net and made necessary changes in the PATH variable, with Oracle client version 10.2.0 path set before the Oracle developer 10.1.0 path, but the problem did not solve.
Ironically Toad is still able to connect through the Oracle 8.1.7 client network information, though it gives warning that the client and server version are different.
Toad is not able to use the latest Oracle 10g client either of Oracle client or Oracle Developer suite network information and is giving OCI error.
Request the Toad experts to provide a work around to resolve the problem.