When connecting to PSM through Firefox, you receive the "Security Warning" popups, but the "Continue" button is not clickable sometimes Java times out and crashes. The issue is intermittent.
Prevent the popup from occuring, by installing a trusted web certificate into TPAM. Ensure the CA certificate is installed onto Java on the workstation, and the FQDN is being used to access TPAM.
Use Internet Explorer instead of Firefox.
Upgrade to 2.5.916. In TPAM version 2.5.916 and later clicking the Connect button on the Request screen prompts the browser to download the JNLP file, which is then launched using Java Web Start (javaws.exe), which mitigates browser issues.