[PROBLEM] CEC stopped working

[Senseohasser]

Hi!

Since some time now my Xbian won't update anymore.

When I run 'apt-get update' I receive the message: 'W: GPG error: http://http.debian.net stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY CBF8D6FD518E17E1'

And when I run 'apt-get upgrade' I receive this:
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
apt apt-utils gettext libapt-pkg4.12 libasprintf0c2 libgcc1 libgettextpo0 libgomp1 libstdc++6 python-apt unattended-upgrades wget xbian-package-xbmc xbian-update
0 upgraded, 0 newly installed, 0 to remove and 14 not upgraded.

Upgrading via the config-tool does not work either

Any ideas?