I'm trying to install a SIS file and get the message "Component failed secutiry check". Does anybody know any reasons of that?

See the "Software installation" option setting in Control Panel/Application manager (it can "On", "Off" or "Signed only"). Turn it "On" to allow installation of unsigned apps.

More in the user's guide.

It's a signed application. i have a symbian developer certificate.
but the security check is failed. how could that be?