unresolved dependencies

[bazrider]

Hullo to every one here. I am bazrider or commonly known as Basile. I am a newbe in ubuntu and in linux in general. Some days ago i had in my upper right corner shown the forbidden (traffic) sign. When i clicked upon it had shown me the following message :
"...Ε:Encountered a section with no Package: header, Problem with Mergelist/var/lib/apt/lists/packeges.medibuntu.org_dists_precise_free_i18n_Translation-el,E:The package lists or status file could not be parsed or opened...". I post here because in the greek ubuntu forum this topic is placed in the "software" section.
What am i asking here is :
1. is this a worrning for a serious malfunction ?
2. can it be fixed ? If yes then in what manner can i fix it ?
3. what may have caused it ?
I have searched in the forum in there was a specific topic about this (unresolved dependencies, but i did not find anything relevant).
Any kind of help shall be wellcome.
Thanks in advance to anybody who "bothers" replie

[Micro]

[bazrider]

Resently i had an unresolved dependency worning on my pc.
It seems like this :

E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/gr.archive.ubuntu.com_ubuntu_dists_precise_main_i18n_Translation-el, E:The package lists or status file could not be parsed or opened..
How can i deal with it ?

[smeterlink]

that worked for me, thx