Netscape 7.1 does not "save image as"

When I try to save an image from one of my newsgroups, I right click the 
image, select > "Save Image As", select the folder, and click "Save". 
But no picture is saved and download manager does not record the 
activity. In fact if I click on "Tools" > "Download Manager", the 
Download Manager screen does not appear.
This has happened before and it seemed to cure itself after a few weeks.
I have no clue what causes it or cures it.
I can download the images using Outlook Express.
Any ideas for a fix.
Bob Williams