DSC Problem and Solution: One Way To Possibly Solve a “Cannot invoke the SendConfigurationApply” Problem

Goal:  You want to use DSC to apply a configuration.
Problem scenario:  When you run the "start-dscconfiguration NameOfConfig -wait -verbose" (where NameOfConfig is the name of the configuration) from the folder that houses the subfolder with NameOfConfig, you get an error like this: "DSC error: Cannot invoke the SendConfigurationApply method.  The sendConfigurationApply method is in progress..."
Solution: Back up and delete the subfolder named NameOfConfig.  You want to delete the .mof files. You'll need to recompile the configurations that are deleted.