Loading applet in second instance of browser causes hang on Linux & Solaris

When trying to load a 2nd applet in a new browser window or
in a different browser session, after another applet has already
been loaded, the browser will hang or crash (with bus error and core dump).

To reproduce on Solaris:
1. setenv NPX_PLUGIN_PATH {JRE}/plugin/sparc/ns4
2. Start Netscape and load an applet
(ex: http://webwork.eng/products/plugin/1.4/demos/applets/Clock/example1.html)
3. In Netscape do File -> New -> Navigator Window
4. Load another applet (can be same) in this new window
5. The applet does not load and at this point it hangs

The problem started in merlin build 71.

This is not a problem on Windows.