When upgrading to version 1.4.x, you suddenly can't access your repository anymore. Every try is rejected with the error message:
OPTIONS of 'path': 401 Authorization Required 'url'
The reason for this is the automatic authentication with SSPI which is activated in version 1.4.x. That means TortoiseSVN now tries to authenticate automatically with the credentials of the user logged on to the Windows domain controller.
If you have set up your server to authenticate with SSPI against a domain controller, and the domain controller does not have the user account GUEST enabled, you should be fine. But if the user account GUEST is active, then all authentication succeeds with that user - and you usually won't give the user GUEST access to your repository. That's why the authentication succeeds, but the authorization fails.
Another reason why it can fail is if you have set up different accounts for the repository access than you use for logging in to your workstations (although then I wonder why you are using SSPI authentication in the first place).
To solve this issue you have the following options: