This error may be related to the browser or Admin server cache.

1). Clear the browser cache. You can achieve this by clicking the “Internet Options” -> “General Tab” -> “Browser History” -> “Delete…” if you are using IE 7 or greater.
2). Stop the Administrator server and the TRA Hawk Agent.
3). Go to the system temp folder (e.g., /tmp or /var/tmp). Delete the folders named as “tibco_<DOMAIN_NAME>_Administrator_<HOST_NAME>_<USER>” and “tibco_<DOMAIN_NAME>_TSM_<HOST_NAME>_<USER>”.
4). Restart the Administrator server and TRA Hawk Agent.
5). Try to open the page again using IE.

Or you could try to open the Admin GUI using another browser (e.g., Firefox / Opera).