Memory problem BeforeDrawThemeObject?

Hi,

my application (build with visual objects 2.8) crashes after a view minutes if I add code for changing some of the cell background colors.
If I remove this code, everything works fine. I'm using the version 13.0 activeX of the calendar control.

Example:

METHOD OLEOBJECT1BeforeDrawThemeObject(eObjType,pCell) class terminplan4
if eObjType = xtpCalendarBeforeDraw_DayViewCell .and. pCell:WorkCell
    self:oDCOLEObject1:Theme:DayView:Day:Group:Cell:WorkCell:BackgroundColor := rgb(200,200,200) // <= application crashes right here :-(
endif   

Any ideas?

Thanks in advance.