Ubuntu :: Update Manager: Installing Untrusted Packages?

i'm getting an error when trying to run my update manager. i had been having a problem updating my opera, but just today my current package isn't downloading. the error i am getting is:

"Requires installation of untrusted packages The action would require the installation of packages from not authenticated sources." the detail info is:

"computer-janitor computer-janitor-gtk empathy empathy-common icedtea-6-jre-cacao icedtea6-plugin libc-bin libc-dev-bin libc6 libc6-dev libnautilus-extension1 nautilus nautilus-data nautilus-sendto-empathy openjdk-6-jre openjdk-6-jre-headless openjdk-6-jre-lib opera ubuntu-docs upstart"

i tried to just ignore that, so i unclicked it (just wasn't interested in dealing with it right away), and go on {this is how i had been ignoring the same error on my opera update for a week or so} --- and so when i tried going on, i got same above error except with this detail:

"empathy empathy-common icedtea-6-jre-cacao icedtea6-plugin libc-bin libc-dev-bin libc6 libc6-dev libnautilus-extension1 nautilus nautilus-data nautilus-sendto-empathy openjdk-6-jre openjdk-6-jre-headless openjdk-6-jre-lib opera ubuntu-docs upstart" ps- i am a pseudo novice who is trying to learn how to use the terminal, so if it's not too much of a pain, i like terminal directions,