In the System Environment Variables, rename the LDAP_ADMIN and ORACLE_HOME (add _OLD in its name) since those are usually not needed.
Also clean up the PATH System Environment Variable and remove the extra entries that are not needed.
Next, open your ldap.ora and sqlnet.ora files in Notepad. If there are blank lines and/or 'notes' lines that are not commented out, it may be interfering with Toad trying to read it. Comment out those blank lines and 'notes' lines by adding a "#" in the beginning of each line. And then save the files.
After the above, restart TDP and re-test the issue.
