An error occurred, please run Package Manager from the right click menu or apt-get in a terminal to see what is wrong. The error message was "Error: Opening the cache "E:Encountered a section with no Package: header, E: Problem with MergeList/var/lib/apt/lists/
security.ubuntu.com_ubuntu.comubuntu_dists_lucid-security_main_binary-i386_Packages, E:The package lists or status file could not be parsed or opened.) |This usually means that your installed packages have unmet dependencies

Welcome.
Did you do that? What happened then?

"This usually means that your installed packages have unmet dependencies"

well? it might be right

you can run dpkg (or apt?) to check (various ways, also various softwares/scripts that do this) and find what software has un-met dependancies

it could be that .../lists/... folder has become corrupted (i'm unsure if you can delete it)

if / when you find out what software it has issues with: remove it (and remove all software that depends on it - should be automatic), and re-install. you might need options to ensure "comlete removal" of the packages old files

if picking a fight with packages doesn't work you'll either have to dig "allot deeper" into the issue or re-install (or load a backup. you have one right?

HOWEVER: a quick warning. do you have an auto-updating system? if so, you have to know what version is current and if the problem is temporary - could be you got shipped a bad dependency file or what OR it could be you have a package installed that the new version "had to remove" (yuk) and it didn't completely do so. i could explain how a packaging system, versioning, an dependency system works but it wouldn't matter since the "new maintainers" made it a "closed system": if you can't use commands to ask software to fix the (dependency table) for you: you can't do it.

you should be able to find a way to run the tool by hand, and when you do read the manpage to find the option for "attempt to repair and continue". that might help.

usually, running the tool by hand, many "fixable problems" are noticed and the commandline software asks the Interactive User / terminal user questions to correct certain issues. (so if you haven't - see if there's a commandline tool like 'dpkg(1)' to use)

I'LL WARN YOU - it can be VERY timely trying to fix APT / depends issues once they crop up. It'd be better to load a backup. Or re-install. Or use an iMac and run a linux tools (even X) under mac BSD.

(don't attempt to fix complex apt issues they only get worse)

You obviously don't use a Debian-based system, so if you don't know, it's better to just say nothing. Do you understand that you're asking the OP to buy an iMAC to solve his problem.

That seems a bit extreme! Apt tools usually work just fine to solve the problem.

And for the OP, I don't think the lucid ppas exist any longer. Post your /etc/apt/sources.list file inside [quote] tags.

Welcome to LinuxQuestions.

As stated lucid (version 10.04 LTS) went EOL depending on version as recently as 2015. The main repositories are no longer available which probably is the reason your having problems. It would help to know what you were doing when the error occurred as well as what you are trying to accomplish.