Do you have console access to the switch, you may want to try remove the ip address completely and then adding it back with the new one.
Hello,   my problem is that I want to change the IP of three S4810 Force10 Switches where two of them buliding a stackunit and one is an edge switch. For the edge switch I could easily change the IP of the ManagmentEthernet, but for the stackunit I always get the Error Message: % Error: Mgmt. IP address(es) and virtual IP address need same mask and subnet This one I get also when I try to change the virtual IP. It also doesn't matter whether the stackunit is connected or not. What can I do?   Example: I want to change one of the Mgmt. Ethernets of the stackunit from 130.170.5.241/24  to 130.170.119.251/24. 
Error: Mgmt. IP address(es) and virtual IP address need same mask and subnet