[noraj]

did you try to do a
/script DEFAULT_CHAT_FRAME:AddMessage(UnitName("PartyN")
for one of the party members thats displayed as Unknown Entity to see if it returns a name
if it does try the code changes below...dunno might help...not so much a solution as a work around(if it works)

function Perl_Party_Set_Name()	--Failed attempt at the Unknown Entity fix
--	       WeirdBehaviorFlag = nil -- this is the flag if we're getting Unknown Entity
                for partynum=1,4 do
--		local partyid = "party"..partynum;
--		local partyname = UnitName(partyid);
--		-- Set name
--		if (UnitName(partyid) ~= nil) then
                        if( partyname == "Unknown Entity") and (not WeirdBehaviorFlag) then WeirdBehaviorFlag = 1 end 
--			if (strlen(partyname) > 20) then
--				partyname = strsub(partyname, 1, 19).."...";
--			end
--			getglobal("Perl_Party_MemberFrame"..partynum.."_NameFrame_NameBarText"):SetText(partyname);
--		else
--			-- do nothing since this should be taken care of by Perl_Party_MembersUpdate
--		end
--	end
--end

I bolded my suggested changes
then in your OnUpdate Handler toss in a
if(WeirdBehaviorFlag ) then function Perl_Party_Set_Name() end -- check the party again if there is an "Unknown Entity"

and see if that gets it to load