Update Error

[Hasan Halym]

After installing Ubuntu 9.10 i keep getting following error with any update
via update manager..

please help

The error is:

"GPG error: http://packages.medibuntu.org karmic Release: The following
signatures couldn't be verified because the public key is not available:
NO_PUBKEY 2EBC26B60C5A2783Failed to fetch
http://apt.wicd.net/dists/Karmic/extras/binary-i386/Packages.gz  404  Not
Found
Some index files failed to download, they have been ignored, or old ones
used instead."
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