File: ConfigurationForm.cs Line: 20 Error: The type or namespace name 'ClassSpecific' does not exist in the namespace 'Singular' (are you missing an assembly reference?) that is what is coming up, how do I fix it?
Most probably cause is that you've installed a new HB version over an old one. But no one can know for sure unless you attach a full log: How To: Attach your HB log file [with pictures]