You might try checking out
http://www.ufaq.org
They have a lot of helpful information about netscape there.

Many Netscape problems can be resolved by deleting the cache folder and history file.

Close all instances of Netscape and then delete
C:\Program Files\Netscape\Users\NAME\cache
where C is the drive that you installed windows in and NAME is the user profile name you use in netscape.
It might be worth doing this to all user profiles.

Also delete the file
C:\Program Files\Netscape\Users\NAME\netscape.hst
again where C is the drive that you installed windows in and NAME is the user profile name you use in netscape.

Netscape will automatically rebuild these when it starts.