If the download file and opening view.jnlp file is taking long like longer 1 minute (guessing here)
I was running into this Login failed or timed out as above. So, I went to the java control panel or recently changed to ControlPanel (linux) and Configure Java (Windows 7), under Advanced tab, select Always allow for JNLP File/MINE Association, select Do not check for Perform signed code certificate revocation checks on and Perform TLS certificate revocation checks on.
This seemed to help overcome the timeout issue quickly.
It was just to the Machine I was using the client on not having access to the internet.
After the Client downloads the JNPL file and then from it downloads the Java JAR files, it attempts to verifies the certs against an oracle Certificate Authority (Checking for cert revocation). Because the machine has no internet access this fails.
But it takes 2 min before this revocation times out and by this time the temp password used (and visable) in the JNPL file has expired.
This issue can be addressed by disabled Cert Revocation checks.
Control Panel -> Java -> Advanced Tab
(note: another workaround is downloading the JNPL file and substituting the temp username & password with the CIMC admin username & password).