TimThumb is a popular image resizing script often used in WordPress themes and plugins to dynamically resize images. However, it's important to note that TimThumb has had security vulnerabilities in the past, and it's generally recommended to use alternative, more secure image resizing methods.

If you're facing issues with TimThumb on a WordPress multisite setup, here are some steps you can take to address the problem:

1. Check TimThumb Configuration:
   

   

   Ensure that the TimThumb configuration (timthumbconfig.php) is set up correctly for your multisite environment. Check paths, cache settings, and other configuration options to ensure they align with your multisite setup.

2. File Permissions:
   Verify that the file permissions for timthumb.php and any related cache directories are set correctly, allowing the web server to read and write to these files and directories.

3. Update TimThumb:
   Make sure you're using the latest version of TimThumb. Check the official repository or the developer's website for updates and security patches.

4. Alternative Image Resizing Solutions:
   Consider using alternatives to TimThumb that are more secure and built into WordPress, such as using the WordPress builtin image resizing functions or utilizing plugins like "Regenerate Thumbnails" to resize images.

5. Debugging:
   Enable debugging in TimThumb to get more information about the issue. You can do this by setting the DEBUG_ON constant to true in the timthumb.php file and checking the logs for any error messages.

6. Check Server Configuration:
   Ensure that your server environment (e.g., PHP version, GD library, image support) is compatible with TimThumb. Check your server's error logs for any relevant information.

7. Security Measures:
   If security is a concern, consider removing TimThumb altogether and utilizing more secure image resizing methods, such as the WordPress native image resizing functions.

8. Consult Documentation and Forums:
   Review the official TimThumb documentation and seek assistance on WordPress forums or developer communities for multisitespecific TimThumb issues.

9. Consider Professional Help:
   If you're unable to resolve the issue on your own, consider hiring a WordPress developer or consulting a professional for assistance with troubleshooting and securing your multisite setup.

Always prioritize security when handling image resizing or any other functionality on your website. If possible, use wellmaintained and secure solutions to ensure the safety of your website and its users.