Hope this is posted in the appropriate section!
Have downloaded muon-1.3.1.tar.bz2. Am at a loss as to installation.
Would appreciate assisstance.

you've dl'ed the source code, thus you need to compile it. you should be looking for the .deb appropriate for your system and is should be available in you package manager

ps - please stop using bold fonts for all you posts

Is not Muon Package manager THE one I need (which needs to be installed), or is it something else?

my best guess as I don't use .deb's nor Kubuntu

To install you can use :
apt-get install --reinstall muon
apt-get install --reinstall muon-installer

Is it your Muon package that's corrupted or maybe the Muon backend file(s) that are corrupted?

if reinstalling doesn't help you should post more detailed information, try running in Konsole and post any error messages.

Thanks for the advice - Muon now works fine.