.Net framework problem

The 3.5 framework update won't download on my computer, giving me different error messages, the most common is error code is 643.

So i tried to manually install and and got this error log:

[06/25/09,17:42:29] Microsoft .NET Framework 2.0SP1 (x64) (CBS): [2] Error: Installation failed for component Microsoft .NET Framework 2.0SP1 (x64) (CBS). MSI returned error code 1
[06/25/09,17:42:38] WapUI: [2] DepCheck indicates Microsoft .NET Framework 2.0SP1 (x64) (CBS) is not installed.
[06/26/09,10:54:42] Microsoft .NET Framework 3.5 (x64) 'package': [2] Error: Installation failed for component Microsoft .NET Framework 3.5 (x64) 'package'. MSI returned error code 1603
[06/26/09,10:54:51] WapUI: [2] DepCheck indicates Microsoft .NET Framework 3.5 (x64) 'package' is not installed.

I'm running Vista business 64. Any help for either problem would be appreciated.

For XP MS says When you try to install an update for the .NET Framework 1.0, 1.1, 2.0, 3.0, or 3.5, you may receive Windows Update error code "0x643" or Windows Installer error code "1603"
So in Vista you have uninstall NET Framework 3.5,clear orphans by using tool Uninstall Microsoft .NET Framework with Aaron Stebner Cleanup Tool » Raymond.CC Blog

and reinstall NET Framework 3.5