yea I would try wiping out everything, re-upload the backup files, and import database via phpmyadmin. Should be back as long as the settings.inc.php points to the same database file name and username/pass.
I just noticed you said you were on 1.4.3. from being on the forum constantly the last 3 days I see people having issues updating from 1.4. It was suggested to update to 1.4.9 first then update again to 1.5. Haven't tried it.
Also if I were you, I would use a test server to update first then test a buying product, especially in Internet Explorer (had a glitch where images wouldn't appear in IE, was easy fix but you don't want it live like I had it)