HELP!!! Self deleating blocked senders list

Help! This is getting very frustrating! I had a large blocked senders list
that I would add to, usually daily. All of a sudden I noticed that each time
I shut down my computer and then restarted it, my blocked senders list was
empty. I don't know why this is happening. I did not add or change anything
during this time. I receive so much unwanted email, the list was the only
thing that made receive any emails worthwhile. Any suggestions would be
greatly appreciated.
Thanks,
Patty