The htmlview component in PocketPC 2003 get frozen when the DTM_ENDOFSOURCE message is passed and, at the same time, the user is dragging the scroll bar.
I have not found a perfect workaround. The not-so-elegant solution is to detect whether the stylus is captured (GetCapture, stylus is captured while dragging the scroll bar) and if so, postpone the message. Unfortunately, this is prone to race-conditions.