"Sorry the changes you made were not saved, please try again". Parental controls error.

I am having a problem (which seems to be a known issue) in relation to setting the parental controls.  When I put in the changes to the controls, I simple receive the above message.  It is therefore impossible to implement the controls that I want for my children.

This seems like it should be something really straitforward, indeed that is what is suggested here:https://www.virginmedia.com/help/security/parental-controls but it just doesn't work.