Maybe your pst file was broken.You can try a popular Outlook recovery
tool called Advanced Outlook Repair to repair your PST file. It is a
powerful tool to recover messages, folders and other objects from
corrupt or damaged Microsoft Outlook PST files.

Detailed information about Advanced Outlook Repair can be found at
http://www.datanumen.com/aor/

And you can also download a free demo version at http://www.datanumen.com/aor/aor.exe

Wangdong