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To update I typed in sudo update-manager -d into terminal and I got this code back (I had to edit the links):

W:GPG error: h.ttp://linux.dropbox.com precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FC918B335044912E,  
W:GPG error: h.ttp://extras.ubuntu.com quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192, 
W:GPG error: h.ttp://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F104610CF0876AC9, 
W:GPG error: h.ttp://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B187F352479B857B,  
W:GPG error: h.ttp://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 86D36DFDE6A250EA,  
W:GPG error: h.ttp://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5A9A06AEF9CB8DB0,  
W:GPG error: h.ttp://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C2518248EEA14886,  
W:GPG error: h.ttp://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C2518248EEA14886,  
W:Failed to fetch h.ttp://ppa.launchpad.net/pmcenery/ppa/ubuntu/dists/quantal/main/source/Sources  404  Not Found,  
W:Failed to fetch h.ttp://ppa.launchpad.net/pmcenery/ppa/ubuntu/dists/quantal/main/binary-i386/Packages  404  Not Found,  
E:Some index files failed to download. They have been ignored, or old ones used instead.
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marked as duplicate by fossfreedom May 14 '13 at 8:00

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1 Answer

Delete the contents of your /etc/apt/sources/list with:

#############################################################
################### OFFICIAL UBUNTU REPOS ###################
#############################################################

###### Ubuntu Main Repos
deb http://....archive.ubuntu.com/ubuntu/ quantal main restricted universe multiverse 
deb-src http://....archive.ubuntu.com/ubuntu/ quantal main restricted universe multiverse 

###### Ubuntu Update Repos
deb http://....archive.ubuntu.com/ubuntu/ quantal-security main restricted universe multiverse 
deb http://....archive.ubuntu.com/ubuntu/ quantal-updates main restricted universe multiverse 
deb http://....archive.ubuntu.com/ubuntu/ quantal-proposed main restricted universe multiverse 
deb http://....archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse 
deb-src http://....archive.ubuntu.com/ubuntu/ quantal-security main restricted universe multiverse 
deb-src http://....archive.ubuntu.com/ubuntu/ quantal-updates main restricted universe multiverse 
deb-src http://....archive.ubuntu.com/ubuntu/ quantal-proposed main restricted universe multiverse 
deb-src http://....archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse 

###### Ubuntu Partner Repo
deb http://archive.canonical.com/ubuntu quantal partner
deb-src http://archive.canonical.com/ubuntu quantal partner

###### Ubuntu Extras Repo
deb http://extras.ubuntu.com/ubuntu quantal main
deb-src http://extras.ubuntu.com/ubuntu quantal main

And see if that works.

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