I have solved the problem.
From Components >> uddeIM >> System
I changed Overwrite Itemid option from no to yes. After several try there was no more error.
Now reply section works fine.
There was also problem with system messages, after sending the system messages same error was occurring.
But now it works fine too.
After sending the system message it redirects to
/index.php?option=com_uddeim&Itemid=0
Post edited by: cyberxxxxx, at: 2008/08/11 05:12