Sorting by the Column TO often doesn't work in Windows Live Mail--How can I fix it?

I have been using Windows Live Mail for quite some time with Windows 7, but can rarely sort the email in my SENT folder by the heading TO--generally it works in the INBOX.  Today suddenly I can sort by that column in my INBOX, but a short while ago I was able to sort by that column in my SENT folder.  What is going on, and how do I fix it?  When I sort by TO, generally the SUBJECT column gets sorted.  Even if I eliminate all column headings except TO it still doesn't sort right.