iTunes is not opening the correct Microsoft OUTLOOK.PST file!

iTunes V10.5.3.3 is finding or storing an outlook.pst file form about a month ago. My calendar, notes, and contacts list are not being updated on my iPhone 3gs when I synch in iTunes. My podcasts, songs, etc. do get updated, but not the latest info entered in the outlook.pst file. I have "purged" my hard drive from all other outlook.pst earlier files - including checking for hidden files. I have verified that the add-in is enabled in OUTLOOK 2010 - it is. There appears to be other people with this same problem who are using Google Calendar as a work-around - they synch Outlook 2010 to Google Calendar and then Google Calendar to their iPhone. Any ideas?