since morning i am facing Problem while connecting through Control Center
from my client m/c to any of the servers.
However through command window i can easily connect/attach to a instance.

the nodes are present on clients m/c

SQL22223N The instance "T0" does not exist on host "Tiger".
Explanation:

The DB2 Administration Server on host "<hostname>" failed to
execute a request because the instance "<instance-name>" provided
in the request does not exist on the host.

incorrect target instance name
edit the instance settings and verify that the target instance name is correct

>db2 list node directory show detail

Node 5 entry:

Node name = T0
Comment =
Directory entry type = LOCAL
Protocol = TCPIP
Hostname = TIGER
Service name = 50000
Remote instance name = T0
System =
Operating system type = WIN

............
if i try to configure Parameters through CC then it gives this problem...
however other details CC is showing properly

but this is the output of command line mode config
In cc - is the information correct ? there are 5 nodes defined
always try : remove db-instance-system and start again with system
discover instance-discover db

i have removed nodes and recreated them as u said and now its working fine as before
... wondering how it all of a sudden got curroupted