add a certificate in soapui 3.5

i'm using soapui 3.5.

i downloaded a certificate from a website (using IE, view this certificate, install it, then export out to a local file idot.cer via IE options->content->certificates->export).

then, i add this certificate (idot.cer) into a project security keystore/certifcate, without passowrd. However, the status shows .

any idea how to do it ?