Thanks very much for responding. I will try to explain.
In MSN Live mail there are folders to store email messages. These are listed to the left of the main in box screen. There are a group of folders which are stored on "My Computer" which only I can access from the computer on which they were stored. There is another group of folders that I can access from any computer after logging in to my email account. The email messages in question are from the folder located on my computer.
After addressing the problem with an MSN technical representative via live chat, and with another tech rep via phone, I was informed that the lost messages are unrecoverable. I'm out of luck, I think. According to my theory, (which doesn't mean much, I'll admit) the messages should still be there. It is the access that is corrupted.
There are many people having similar problems. I base this on the number of posts on the MSN Live forum. I think MSN screwed up. Regretably, I don't know enough to fix it.