Can’t install .net 3.5 sp1 on windows server 2008

[admin]

I am trying to install subtext via the Web Platform Installer on my Windows server 2008 VPS.

To install it I need the .net framework version 3.5 SP1. It actually fails definetly each time I try, so I tried to install the SP1 manually. I failed with the error message :

Code:
[11/30/09,02:40:01] Microsoft .NET Framework 2.0SP1 (x64) (CBS): [2] Error: Installation failed for component Microsoft .NET Framework 2.0SP1 (x64) (CBS). MSI returned error code -2147467262
[11/30/09,02:40:05] WapUI: [2] DepCheck indicates Microsoft .NET Framework 2.0SP1 (x64) (CBS) is not installed.
When I tried to install the .net 2.0 SP1 x64 it says that it is not supported by vista (?!). I tried to clean up every .net version of my server using the cleanup tool and then install the 3.5sp1 back (and even 2.0sp1) both failed with same error codes.

I am not able to use the Windows update since it is a virtuozzo VPS (and it is said that if I use Windows update it will break my VPS because updates are streamlined by Virtuozzo... ) but the windows update service is started.

Currently the versions installed are :

- .Net 2.0.50727.1434
- .Net 3.0.4506.648

Any hints on solving this issue ?