Under the ISX Manager's System Management--->Network---->Network Settings menu, once originally configured, the fields listed below will not accept any changes.
Gateway, Subnet Mask, Domain Name, Primary DNS, Secondary DNS,
There are two ways to correct this issue.
1) Upgrade the ISX Manager to at least version 4.3.
2) Change the IP address in addition to making the desired changes that need to be made to any of the fields listed above. This will force an ISX Manager reboot. Upon reboot the new settings for any and all of these fields will be updated. The IP can then be changed back to its original address if desired. Changing the IP for a second time will necessitate a second reboot.