I would recommend scanning your PST file for errors first. With Outlook
closed, do a file/folder search for scanpst.exe. Double-click it and follow
the instructions. It will ask you to browse to your PST file though so you
should unhide all hidden files and folders first plus enable the view of
known file types. You can do this in Windows Explorer (Tools > Folder Options
View tab). Scan the PST repeatedly if required (if it finds errorrs, when
the scan is complete then scan again. Then try opening Outlook again.
If that doesn't work, create a new Outlook profile and associate it with
your PST file:
http://www.howto-outlook.com/faq/newprofile.htm
Please let me know how you make out.