Outlook 2003 Junk Filter marks everything as junk mail

[Larry]

I was using the junk mail filter successfully for a while in 2003 and
then for some reason (and I didn't make any changes that I can recall)
it started to mark everything as junk, safe senders, safe domains etc.
The only mail that doesn't get marked as junk is mail that has another
rule on it like if it's from a certain sender to put it in another
folder

I have applied the latest updates and tried all junk mail settings
from the most safe to most aggressive and the behaviour is the same

Any ideas? It's unworkable like this since I am sure I am losing mail
in the junk mail folder. Would a reinstall fix it or are the rules
embedded in the PST File?

Thanks

Larry