I was trying to install skype (which is now completed, so this is now irrelevant), but when I was adding the archive.canonical.com repository to install Skype, it apparently caused an error in the Sources.list file (/etc/apt/sources.list) that prevented me from using apt-get, Ubuntu Software Center, and the Software and Updates manager (system settings). I managed to fix this error so now I can use apt-get commands again, but now I still can't use Ubuntu Software Center or the Software and Updates manager (system settings) and I get the following error message every time I turn on my laptop:
"Opening the Cache (E:Opening /etc/apt/sources.list - ifstream::ifstream (13: Permission Denied), E:The list of sources could not be read., E:The package lists or status file could not be parsed or opened.) This usually means that your installed packages have unmet dependencies"
I am using Ubuntu 13.04 and if it's relevant, I recently removed some libraries using the Remove Orphaned Packages app.
I DON'T KNOW WHAT TO DO TO FIX THIS PLEASE HELP.