Im an Outlook 2010 user, and this does not happen to my program connected to exchange. When you create an appointment, that has a start time and a finish time, what is your default calendar view as weel as the time zone you set the appointment?\

Also are you setting it in the proper Calendar?

When you have a shared calendar unless you have the proper permissions to add or edit events, you will not be able to add appointments.

Keep me posted.