Today while busy with SCCM and SCOM 2012 installations the feature Dotnetframework 3.5 needs to be installed.
Initially by selecting the feature and choosing install it fails at 50%.
Quick fix is the point to an alternative location and choose the DVD where the files are located and add the following: D:sourcessxs or your drive letter and then start the installation.
Installation went through with no issues on both SCCM and SCOM servers.