Now have a red circle with a white dash horizontally in the middle (almost like a do not enter sign) in the bottom left hand corner of the screen. It's all to do with a 'serious error' so it tells me about it's inability to update itself (security updates etc)

Here's the message:

E:Encountered a section with no Package: header, Eroblem with MergeList /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_precise-security_main_i18n_Translation-en, E:The package lists or status file could not be parsed or opened.

I'm a bit of a newbie... enjoy Lubuntu because of it's small footprint... could somebody take the time and trouble to explain in plain english what i need to do

Many thanks in advance