serioius problem with package manager

[G.]

I noticed a warning on the top bar (Ubuntu 12).  It says an error
occured, please run package manager.  I did so an got the following:

E: Encountered a section with no Package: header
E: Problem with MergeList
/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_precise-security_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.

Googling that I got
https://answers.launchpad.net/ubuntu/+source/update-manager/+question/197658
 which gives instructions.  I am writing here to see that this is the
correct thing to do.

Or http://www.ihaveapc.com/2011/05/how-to-fix-problem-with-mergelist-varlibaptlists-error-in-ubuntu-11-04/?
 Much simpler.

thanks

garyk