Problem with IP address in my switch

I've a Switch which i had already set to IP address 192.228.168.071,usually i can ping
my switch IP address succesfully and used the telnet to access my switch console through my remote
workstation to view all the configuration.But unfortunately recently when i tried to ping my
switch ip address 192.228.168.071 it automatically displayed out message saying 192.228.168.57
unreacheble.I've a Win2000 DHCP server in my network where the IP address 192.228.168.71 already
been excluded from the DHCP clients address.I can access my switch through the direct connection
using RS-232 cable.
Please advise what action should I take to counter this problem.
Thank you.