If you currently run on a RHEL 4.7 host, it is highly advised to move your VNC session(s) to a RHEL 5.X host.
You can check what version of Linux you are running by entering, "cat /etc/redhat-release"
If you see the following you need to move to a new host:
Red Hat Enterprise Linux WS release 4 (Nahant Update 7)
Other Xilinx software, such as Project Navigator, that is not JAVA based will continue to run on RHEL 4. However, RHEL 4 will not be an officially supported platform for any of the ISE Design Suite 14.1 tools.