The value or range you are adding has already existed. The report appears to have been saved 'With Data' (which it is not saved with data) or you are attempting to 'Use saved data' when the report has not been saved with data.
For 'With Data' reports, you cannot enter parameter values as the report must run with the data embedded in it.
This is what I want it to do, I did uncheck the option to 'use saved data', but it still didnt work...To enter partameter values and have CRD repopulate the report with fresh data each time, save the report again without data and uncheck the option in CRD to 'use saved data'. Can you help? thanks

Did you refresh the schedule after unchecking the "Use Saved Data" option? CRD does not see the change to your reports until you refresh the schedule.

yes, i refreshed, schedule refreshed ok, and I can preview the report, just cant execut, thanks

I see from the history page that there was a problem with copy/paste of schedules and this has been resolved in a very recent build. Have you tried downloading the latest build?

Its worth signing up on the history page to get automated updates when a new version is released too if you haven't already done this.