I think the TS Calendar only synchronizes with the events in the "HPTouchSmartCalendar" within Vista Calendar. Since the Vista Windows Calendar can show several "secondary" calendars at the same time, it is possible that your events are in a different "secondary" calendar than "HPTouchSmartCalendar".

That is, you might want to check if:
other user's TS Calendar other user's Vista Cal:HPTouchSmartCalendar
other user's Vista Cal:SecondaryCal your Vista Cal:PrimaryCal
and not
other user's Vista Cal:HPTouchSmartCalendar your Vista Cal:PrimaryCal

When you enter your events into your calendar, do they show up on the other user's Vista Calendar if the other user tells Vista Calendar to hide the "HPTouchSmartCalendar"? If so, then Vista Calendar is putting your events into a different calendar and not in the "HPTouchSmartCalendar".

Hope this gets you a little further. :)