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I am getting the following error message when the update manager runs:
Apt Authentication issue
Problem during package list update. The package list update failed with a authentication failure. This usually happens behind a network proxy server. Please try to click on the "Run this action now" button to correct the problem or update the list manually by running Update Manager and clicking on "Check".
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://linux.dropbox.com lucid Release: The following signatures were invalid: NODATA 1 NODATA 2
W: Failed to fetch http://linux.dropbox.com/ubuntu/dists/lucid/Release
W: Some index files failed to download, they have been ignored, or old ones used instead.
This error started to appear recently and for no obvious reason (maybe because I created myself a private PGP key?). I'm running Dropbox v0.7.11 on Ubuntu Lucid 10.04.