There seems to be a problem with BusinessHoursNoScroll and Full modes in IE6. See also
http://forums.daypilot.org/Topic.aspx/189/bug_move_event_with_ie6.
Unfortunately, I haven't been able to find a solution yet.
I believe it's caused by the main div that contains the scrollbars (using overflow:auto). Originally, I wasn't adding overflow:auto in the modes that don't show the scrollbar. However, that caused weird problems in IE7 (
http://forums.daypilot.org/Topic.aspx/212/calendar_control_hides_events_in_ie7). Now it uses overflow:auto for all modes but problems appeared in IE6...