Netscape 4.51 bug?

[BROWNH]

When I pulled down Netscape's bookmark menu, I lost keyboard input or
mousebutton input. I.e., I could move the mouse pointer, but do nothing.
The keyboard worked (Caps lock light, for ex), but had no effect. The
operating system and desktop were not hung (The Gnome clock continued to
click off the minutes). Apparently Netscape blocks any inputs, and so I
had no choice but to RESET.

Is this a known Netscape bug?

Haines Brown