Quest SQL Optimizer 8.5.0 for Oracle

I am having problem with database connection, SQL optimizer showing me the below error during the connection:

ORA-12154: TNS:could not resolve the connect identifier specified

I am using Quest for Toad with no problem with the same TNS set up.
Please advice.
Thanks - Shahriar

I have the same problem


Are there more than 10 Oracle clients installed in your pc? What Oracle clients did you choose to connect? Installed or Instant client?