Thanks for reporting the problem. It seems that the JavaScript causes some problems in your case. It seems like a bug that might appear under specific conditions .
A few questions:
1. What version of Windows and IE are you using?
2. Does it happen always or just sometimes?
3. What control is causing the problem - DayPilotScheduler or DayPilotCalendar?
4. Do you have a different machine where you can test if it's doing the same?
5. Is the demo (
http://www.daypilot.org/demo/Calendar/) working fine in the same browser?