You should be able to reproduce the problem even on the Telerik demo for this control at the following link:
http://demos.telerik.com/aspnet-ajax/calendar/examples/datepicker/custompopup/defaultcs.aspx
Just click the button and select a date multiple times. I'm not sure precisely what is triggering it because it doesn't happen all the time. I've attached an image with the problem.
Thanks,
Dave
6 Answers, 1 is accepted
Thank you for contacting us and for your question.
The bihaviour you described is a known issue for the RadCalendar control. We are aware of this problem and our developer are actively working on its resolution. We will inform you as soon as the problem is resolved and appropriate hotfix will be provided.
Regards,
Maria Ilieva
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking system and vote to affect the priority of the items.

I'm interested did this issue get resolved?
Also I want to add that I experience the same behavior with RadDateTimePicker:TimeView but only under IE7. Tested with FF 3 and IE 8 and they work fine.
Plamen Petrov
Application Software Systems
It seems that this bug is rather complex and it will take some more time to be fixed. I already increased its priority and our developers are actively working on it. As soon as fix is available I will send you a hotfix to apply.
Thank you for your patience and cooperation.
Regards,
Maria Ilieva
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking system and vote to affect the priority of the items.
I'm glad to inform you that the issue was fixed and the fix is available in the latest internal build which you could download from your account. Test the application with the hotfix and let me know if further assistance is needed.
Thank you once again for your patience
All the best,
Maria Ilieva
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking system and vote to affect the priority of the items.

Plamen Petrov
Application Software Systems
I'm glad that the problem has vanished, however I suggest you to upgrade to the latest internal build as there were the same issues with the other calendar controls and they were fix in it.
Best wishes,
Maria Ilieva
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking system and vote to affect the priority of the items.