Well, I wasted a perfectly good day on this one. Happily, I found a solution.
Here’s the problem: when you install the Linux version of Netscape 6.1 on top of a basic “workstation” or “desktop’ installation of Linux (in my case Mandrake 8.0), even if you select that Java and Flash plugins should be installed along with the browser, when you start up NS they don’t work. It’s maddening because the plugins are in the right spot, but Netscape doesn’t seem to be able to “find” them there.
Here is the solution: using your favorite package manager software (in my case rpmdrake, aka MandrakeUpdate), install a package title “XFree86-devel”. This package includes a library file called “libXt.so” that Netscape 6.1 depends on to figure out what plugins it’s got installed. Fortunately, the XFree86-devel package comes on disk 1 of Mandrake (and I assume most other distros as well) so this is no big deal–it only takes about 30 seconds. But it’s the only way that I was able to get my Flash going in Netscape 6.1. What a joke–you’d think that they might have caught that before they made the final version available for download.
In any event, I hope this helps somebody else avoid spending a bunch of time solving what is basically a pretty easy problem, once you’ve figured it all out.
Good Luck!