Hi Dushan,
What version of LUA are you using? Is it LUA 2.3?
Check out the details of the task in Activity Monitor. What is the status for each file? If the Distributin Center already had a copy of that file, it will say "already present on the server." There will be a similarly informative status for other files.
Regarding the Downlaod, I had a similar behavior yesterday -- repeated attempts to download SEP definitions failed, always on the same file. I am checking now to see if the download will complete.
All the best,
Mick