when i try to update i see this erroIgn http://ppa.launchpad.net quantal
InRelease
Ign http:*//archive.canonical.com lucid InRelease
Ign http:*//security.ubuntu.com quantal-security InRelease
Ign http:*//ir.archive.ubuntu.com quantal InRelease
Ign http:*//ppa.launchpad.net quantal InRelease
Hit http:*//archive.canonical.com lucid Release.gpg
Hit http:*//security.ubuntu.com quantal-security Release.gpg
Ign http:*//ir.archive.ubuntu.com quantal-updates InRelease
Get:1 http:*//dl.google.com stable InRelease [1,540 B]
Hit http:*//ppa.launchpad.net quantal Release.gpg
Hit http:*//archive.canonical.com lucid Release
Hit http:*//security.ubuntu.com quantal-security Release
Ign http:*//ir.archive.ubuntu.com quantal-backports InRelease
Ign http:*//ppa.launchpad.net quantal Release.gpg
Hit http:*//archive.canonical.com lucid/partner Sources
Hit http:*//security.ubuntu.com quantal-security/main amd64 Packages
Hit http:*//ir.archive.ubuntu.com quantal Release.gpg
Get:2 http:*//dl.google.com stable Release.gpg [1,540 B]
Ign https:*//private-ppa.launchpad.net quantal InRelease
Hit http:*//ppa.launchpad.net quantal Release
Hit http:*//archive.canonical.com lucid/partner amd64 Packages
Hit http:*//security.ubuntu.com quantal-security/restricted amd64 Packages
Hit http:*//ir.archive.ubuntu.com quantal-updates Release.gpg
Ign http:*//ppa.launchpad.net quantal Release
Hit http:*//archive.canonical.com lucid/partner i386 Packages
Hit http:*//security.ubuntu.com quantal-security/universe amd64 Packages
Get:3 http:*//ir.archive.ubuntu.com quantal-backports Release.gpg [933 B]
Get:4 http:*//dl.google.com stable Release [1,540 B]
Ign http:*//dl.google.com stable Release
**E: GPG error: http://dl.google.com stable Release: The following signatures were invalid: NODATA 1 NODATA 2
r**
thank you before your answer
