Try checking to see if the properties for auto refreshing the data when you open the workbook are set. This can be set to automatically open the required spreadsheet(s)/data file without user intervention. I use this to get data from the web automatically when I launch a workbook for epos data to be collated.
I am not exactly sure why the 2nd problem occurs, but if you change data on the source you might have to select the manual refresh from the toolbar to get it to update. This could be because the source is only checked when opening the workbook with the pivot on. Have you tried to set the automatic refresh frequency period, or is it set to only get data on opening.