This bug has already been fixed and is scheduled to be released with the service pack. The problem is not in a provider and therefore by creating a new one you were not able to fix the problem.
The problem is on both admin side and public side with the calendar view, because the query parameters are not sending the correct start/end dates. Namely, start/end is always the first day of current month / last day of current month, when it should be first visible date in RadScheduler / last visible date in RadScheduler. While there is no way to create a workaround on the admin side, you can create your own public control and use the provider to work around this issue.
I apologize for the inconvenience and the frustration this bug has caused you. If we can help you in any other way, please do not hesitate to contact us again.
the Telerik team