Probably why its freezing.
Okay, try compacting the pst.
What version outlook, internet or corporate mode?
Do you have a mail icon in the control panel? Open it, see if you can get to the properties of the personal folders, and look for a compact option.
Another option is to run scanpst.exe, just search your hard drive for it, you might have to search hidden folders. Point it to your pst, and let it check for errors.
Matt J.
Please always take the time to backup any and all data before performing any actions suggested for ANY problem, regardless of how minor a change it might seem. Also test the backup to make sure it is intact.