Hi Dejo Savicevic,
Thank you for contacting us. Yes in the past we had issues when using a large number of appointments. We believe that the issue is addressed in our latest release - Q2 2010 SP1. I noticed that you have downloaded an old version of RadControls for WinForms. I recommend that you try the latest one and share your feedback. We will appreciate that.
If the issue continues to appear, please send us your application so we can test and locate the issue.
I am looking forward to your reply.
the Telerik team
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