Trouble installing SQL Server 2008 Enterprise Edition on Windows Server 2008 Ent R2

Yesterday I have installed Windows Server 2008 Ent Edition R2 -x64 and have enable application role on it, enable windows update (run and installed suggested updates). I have also verify the .Net framework and it shows that I have .Net framework 3.5.1 is installed on my system.
When I tried installing SQL Server 2008 Ent edition-x64 on this system it fails saying Microsoft .Net Framework 3.5 installation failed, SQL Server 2008 Setup requires .Net Framework 3.5 to be installed
I have searched a lot and find nothing that help me overcome this issue, the only thing that sounds promising me is to download new ISO for SQL Server 2008 Ent Edition. I have already gone through http://social.msdn.microsoft.com/Se...) site:microsoft.com&rn=All SQL Server Forums
Can anybody give me more pointers!!!

Update: Installing with newly downloaded ISO image I was able install SQL Server 2008 Ent x64