Strange problem with Firefox -> all links point back to same page

[98 Guy]

This is Firefox 2.0.0.20.

I typically have many Firefox instances or windows open at any one time
(5 to 10 maybe). I tend to open a link "in a new window" instead of
opening in a new tab or just following the link in the same window. I
do this because it's faster to close the new instance or window when I'm
done with the page rather than hit the back button to go back to where I
was.

Something that's been happening over the past few months is that I'll
click on a link on a page but all it does is re-load the page I'm on.

When I hover over the link, I notice that instead of showing the "real"
link (in the bottom window-bar) it shows the URL of the page I'm on. So
clicking on any link on the page will simply re-load the page.

It's an interesting trick, but I'm getting tired of it.

If I close all firefox windows and start fresh, the problem goes away
(for a while anyways).

Any ideas what causes this behavior?