I tracked this down to the RcfClient<> using virtual inheritance. If you comment out the virtual in this line in RCF\include\RCF\Idl.hpp, around line 87:
, your code should compile and work. The 'virtual' was originally put in in order to support deriving from multiple RcfClient<> classes, but that's not really relevant any more. You can remove it without any ill effects.