Task List Problem

Hi,

We're using K2 .NET 2003 with SP4 and we're facing a problem about Task List on SPS.

We cannot retrieve Task in the Task List in SPS. I found the following log on the server console:

Error 4430 Error resolving all rights for The format of the specified domain name is invalid Resolving User:NT
Info 4401 Authenticated NT AUTHORITYANONYMOUS LOGON at 192.9.220.28 using NTLM
Info 6005 K2ROM Marshal: OpenWorklist2 for NT AUTHORITYANONYMOUS LOGON at 192.9.220.28
Info 6016 Opened Worklist of 0(20 Bytes) Items in 0:0.15 for NT AUTHORITYANONYMOUS LOGON at 192.9.220.28

I guess because the server get the NT AUTHORITYANONYMOUS (Cannot get the right person) user for retrieving the task list, so the task list is empty. However, if I logon to the server that host the SPS, and check with the task list, the K2 console can get the right person to logon to the SPS.

Is it a must to use Kerberos Authenticaton in SPS?

What is the web service that the Task List calling?

Many thanks.

Kind Regards,
Zoe