I consistently get these errors when either clicking the "check" button in the update manager or running sudo apt-get update from the command line:
I have tried every solution on the forums and otherwise found by google for this. I actually used to get a lot more errors, but this is what I'm left with.
W: GPG error: http://archive.canonical.com lucid Release: Unknown error executing gpgv
W: GPG error: http://ppa.launchpad.net lucid Release: Unknown error executing gpgv
W: GPG error: http://archive.ubuntu.com lucid Release: Unknown error executing gpgv
W: GPG error: http://archive.ubuntu.com lucid-updates Release: Unknown error executing gpgv
W: GPG error: http://archive.ubuntu.com lucid-security Release: Unknown error executing gpgv
Working on a hunch (one of those hunches where you can't quite explain how you actually came to this conclusion), I downloaded the source code for the C++ readline library v. 6.0, recompiled, and replaced the old libreadline install with my new files. That got me down to a single error:
... which I then fixed using the solution posted in the threads pertaining to what to do for a missing PUBKEY.
W: GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5A9BF3BB4E5E17B5
That seemed to do the trick, and now I can upgrade. Thanks for your help.
(Of course, this makes me wonder -- how many of those persistent gpgv errors popping up maybe have something to do with a bad readline library?)