This affects Redhat 5.9:
When multiple netscape browser windows are open, and the
user closes one of them (i.e. with File->Close or by
clicking on the window's close button), then netscape
crashes and all open windows immediately close. The reported
error (at stderr) is "Bus error".

This problem also occurs when the user does File->Exit in
netscape, regardless of how many or few browser windows are
open.

The end of an strace when netscape crashes looks like this:
gettimeofday({922103651, 642529}, NULL) = 0
gettimeofday({922103651, 647846}, NULL) = 0
gettimeofday({922103651, 650471}, NULL) = 0
--- SIGSEGV (Segmentation fault) ---
getpid()                                = 20175
kill(20175, SIGBUS)                     = 0
--- SIGBUS (Bus error) ---
+++ killed by SIGBUS +++

This occurs in both the Netscape 4.08 package included with
Redhat 5.9, and also Netscape 4.50.

Perhaps this is related to bug #1485.