Thanks Cactus .. How do I know which contrib is at fault?
That is a hard thing to say unfortunately. The encoding type is not listed in the locale files. Did you already do the update against SME Contribs to drag in all correctly encoded contribs available? It should fix some (maybe all if you have only some common contribs (like from dungogs free repository)
also how do I remove the offending contrib?
Removing packages is always a tricky task, but it can be done from the SME Server shell. Using yum remove is a way, but might impose the risk of deleting stock SME Server packages (rule of thumb, when the list of dependencies is really long and contains packages starting with e-smith or unfamiliar packages starting with smeserver or having some stuff in them that vaguely reminds you of SME Server lexicon you should not uninstall that way). You should instead try and see what dependcies can be removed manually without damaging the system using 'normal' rpm query commands like rpm -q --whatrequires ... and rpm -q --requires before removing them one by one using rpm -e. Again be very careful as removing to much might leave your system in an unknown and unadministrable state. Best is to keep the latest ISO on CD and backups at hand and when things go AWOL do a CD update to restore all needed packages (it should not override or remove databases and configuration settings, only restore packages accidentaly removed).
and finally as I actually use all these how do I know what is truely compatible before installing in the future?
Again not easy, best option is a VMWare test environment or some other test box. For a rule of thumb you can safely install contribs listed in SME Contribs repository, also all SME Server packages released from now will (most likely as I can not predict the future) be in UTF-8 encoding.