The problem may be due to the corruption of pst file or over sized 2 Gb Pst file size limit. You can use Inbox repair tool to repair your corrupted file.
To run Inbox repair tool you have to locate pst repair file. The pst repair file by default is located at:
C:\Program Files\Common Files\System\Mapi\1033\
Or
C:\Program Files\Common Files\System\MSMAPI\1033
For outlook 2007 scanpst.exe file is located at:
C:\Program Files\Microsoft Office\Office12
For more information visit
http://repair-pst.blogspot.com/
If your pst file is badly corrupted in this situation you can use outlook pst repair software.
The pst recovery software is easy to use and provides powerful recovery solution. You can download the free demo version from the site
http://www.repair-outlook-pst.com/
demo version you can preview 5 e-mails, 20% of contacts and calendar entries from which you can evaluated the efficiency & recovery capability of the software.