Error - WARNING in 12.10

Im a fairly new Ubuntu user so forgive me for some of my ignorance! I am getting an error alert on my computer - it reads

An error occured, 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/
bw.archive.ubuntu.com_ubuntu_dists_quantal_main_i1 8n-Translation_en%5fGB, E: The package lists or status file could not be parsed or opened.)'. This usually means that your installed packages have unmet dependencies

but wen i try to run Synaptic it crashes and gives me the following error message

E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/bw.archive.ubuntu.com_ubuntu_dists_quantal_main_i1 8n_Translation-en%5fGB
E: The package lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.

and then exits

I dont know what to do at all

Try remove that file
/var/lib/apt/lists/bw.archive.ubuntu.com_ubuntu_dists_quantal_main_i1 8n-Translation_en%5fGB
(should be safe to delete but I recommend you just move or rename it).
Then update the package list, either with synaptic or in terminal "apt-get update"