I tried the alternate way of downloading the program, when i enter all the necessary details and select next OSD continues as per normal.

when it comes to phase of adding the computer to the domain it failed again, entered the necessary details and OSD continues fine.

I am sure my problem has something to do with the account winPE/SMS is using to connect to the network path and to add the machine to the domain.
I checked in the SMS console and the network access account is set on the primary server - site settings - Component Configuration - Software Distribution.
This account is not set on any of the Secondary Sites, so it should filter down to the DP/Sec server in question.