Netscape contains very serious memory leaks. If left unattended on a page with autorefresh (like our incoming queue page at Linux-Support.net), it will consume memory and swap until nothing is left. On my system, leaving netscape open for four hours on a page that refreshes every 60 seconds, fills out the remainder of my 128MB of RAM and 128MB of swap, causing a panic (although nothing is logged, and being in X-windows, I'm unable to see anything). Userspace simply dies, while ping's and other kernel-only functions remain intact. I have a test technician account that I can make available for anyone who wishes to duplicate the bug. One potential work around I am currently testing is to add "ulimit -d 32000" to /usr/bin/netscape to keep its consumption under control.
What version of Netscape are you using. I have seen a considerable improvement in the leakage problem with release 4.61-1.
netscape-communicator-4.6-1 As provided in the updates to RedHat 6.0...
you might also try upgrading glibc to the latest version in Raw Hide; there were memory leaks in some of the host resolution code; a process that auto-refreshed would certainly run into this.