i can't cancel or suspend a process in progress .

i launch a process with some activity and one human activity. The task of process were terminated but the process still in progress. In Nwa i see the process is blocked in a last automated activity that invoke a external web service (maybe the web service isn't working well). Now i want to kill this process but when i select it and try to cancel o suspend (throught manage process in nwa) it tell me:

Message:  Error during the process.Number and instance Id's of the processes which can not be canceled  1: ,841705c6-651d-11e0-b317-0000002edcae

Date:  2011-04-13

Time:  10:22:47:179

Category:  /Applications

Location:  com.sap.tc.bpem.nwa.processmgmt.procmgmt.procmgmt.ProcMgmt

Application:  sap.com/tc_lmitsam_uimainframe~wd

Thread:  Thread[HTTP Worker [@28699373],5,Dedicated_Application_Thread]

Datasource:  j2ee\cluster\server0\log\applications_00.log

Arguments:  

Dsr Transaction:  87510d4c65a611e0afc30000002edcae

Message ID:  com.sap.

Session:  1885

Transaction:  

User:  superadmin

TimeZone:  +0200

Customer Msg Component:  BC-BMT-BPM-MON

DC Name:  sap.com/tc_bpemnwa~processmgmt

Correlation ID:  3071150000000004

DSR Root Context ID:  5D6A75C265A611E0BACD0000002EDCAE

DSR Connection:  87510d4c65a611e0afc30000002edcae

DSR Counter:  0

Log ID:  005056A927930AF60000000100000C5C

Host:  SITA1801WZ

System:  CE1

Instance:  J00

Node:  server0

now, what can i do to delete that process?