Hi im using preauth to access to Zimbra from a direct url (Not with SOAP).

Everything was working fine, but lately i've been getting the following error:

Code:
HTTP ERROR: 400

authentication failed for jsmith@domain.com

RequestURI=/service/preauth

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But when I copy the exact url that is trying to open Zimbra on an iframe and paste it on a browser window it load perfectly!

Anyone have anyidea why this could be?