While using the package manager or trying to install applications through Terminal, it is possible to get a nasty error which is something like this :

E:Encountered a section with no Package: header,

E:Problem with MergeList /var/lib/apt/lists /us.archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages,

E:The package lists or status file could not be parsed or opened.

This  will prevent from  installing or upgrading any application in  Ubuntu 11.04.  Fortunately, the fix is simple for this.

From the Terminal type the following commands :

and

This  will delete the older entries and download the latest ones after which the error should no longer be there.

[ In fact, to avoid remembering these commands, they can be put in a shell script and only that script needs to be executed. Check out this post on how to do that.]

Cheers.