[SOLVED]Missing signatures

[parths]

So I got this following error while updating LM 14 today..

An error occured
The following details are provided:

Code: Select all

W: GPG error: http://dl.google.com stable Release: The following signatures were invalid: BADSIG A040830F7FAC5991 Google, Inc. Linux Package Signing Key <linux-packages-keymaster@google.com>
W: GPG error: http://archive.canonical.com quantal Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: GPG error: http://ppa.launchpad.net quantal Release: The following signatures were invalid: BADSIG 8CA7A6E8E4FA953A Launchpad 0 A.D.
W: GPG error: http://archive.ubuntu.com quantal Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

I tried a solution given by the first answerer to the question here : http://askubuntu.com/questions/127326/h ... g-gpg-keys

But it didn't work. I want to know why is this problem arising and how do I resolve it?

[parths]

Found a solution, given by 2F4U given here : http://ubuntuforums.org/showthread.php?t=1983220

I'm still wondering what caused this problem