"ORA-12705: Cannot access NLS data files or invalid environment" when trying to login with Toad. (28370)

User was able to use Toad and connect to the database until they installed a Window's Language support pack. Now user is unable to login to the database using Toad but is able to login through other applications. User gets the following error message:

"ORA-12705: Cannot access NLS data files or invalid environment specified"

RESOLTUION 1:

1. Shut down Toad for Oracle.
2. Open Registry Editor. (Go to Start | Run | "regedit").
3. Browse to your Oracle Client directory. Locate your Oracle Home.
4. Rename the NLS_LANG parameter to NLS_LANG_OLD.
5. Restart Toad and connect to the database.

RESOLUTION 2:

Set up an environmental path variable NLS_LANG:

1. Right click on 'Computer' and select 'Properties'.
2. Click the 'Advanced System Settings' link on the left.
3. Click 'Environment Variables'.
4. Under the 'System Variables' (lower pane), select 'New'.
5. Enter "NLS_LANG" for the 'Variable Name' and "AMERICAN_AMERICA.WE8ISO8859P1" in the 'Variable Value' boxes.
6. Click OK for changes to take effect.
7. Reboot your PC, and re-test the issue.

* Note: It is specified here to use AMERICAN_AMERICA.WE8ISO8859P1, but any NLS_LANG setting can be chosen.

Disclaimer : Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 "Description of the Microsoft Windows registry".

The .NET docs also note this for the ORA-12705 error:
Oracle Client software requires that you give the Authenticated User privilege to the Oracle Home by following these steps:

1. Log on to Windows as a user with Administrator privileges.

2. Launch Windows Explorer from the Start Menu and navigate to the ORACLE_HOME folder. This is typically the "Ora92" folder under the "Oracle" folder (i.e. D:\Oracle\Ora92).

3. Right-click on the ORACLE_HOME folder and choose the "Properties" option from the drop down list.

4. Click on the "Security" tab.

5. Click on "Authenticated Users" item in the "Name" list (on Windows XP the "Name" list is called "Group or user names").

6. Uncheck the "Read and Execute" box in the "Permissions" list under the "Allow" column (on Windows XP the "Permissions" list is called "Permissions for Authenticated Users").

7. Re-check the "Read and Execute" box under the "Allow" column (this is the box you just unchecked).

8. Click the "Advanced" button and in the "Permission Entries" list make sure you see the "Authenticated Users" listed there with:

Permission = Read & Execute
Apply To = This folder, subfolders and files

If this is NOT the case, edit that line and make sure the "Apply onto" drop-down box is set to "This folder, subfolders and files". This should already be set properly but it is important that you verify this.

9. Click the "Ok" button until you close out all of the security properties windows. The cursor may present the hour glass for a few seconds as it applies the permissions you just changed to all subfolders and files.

10. Reboot your computer to assure that these changes have taken effect.

Re-execute the application and it should now work.