When attempting to install or update an instance of WebSphere Application Server (WAS) on a 64-bit operating system, the following messages can be encountered:

• Failed : Your operating system failed the prerequisites check.
  A supported operating system was not detected. Support for your operating system might have been added after the release of the product. You can continue with the installation, but the installation might not succeed.
• Install, com.ibm.ws.install.ni.ismp.actions.PopulateMultipleMaintenanceSelectionPanelAction, msg1, 6.1.0-WS-WAS-LinuxX64-FP0000023.pak. A supported platform, operating system, related operating system architecture, and bit architecture were not detected. For example, a 32-bit product for a specific operating system and operating system architecture must be installed onto a 32-bit installation with the same operating system and operating system architecture. Similarly, a 64-bit product for a specific operating system and operating system architecture must be installed onto a 64-bit installation with the same operating system and operating system architecture. Install a product that has the platform, operating system, related operating system architecture, and bit architecture which is supported by the existing installation

To resolve this issue, it is required that the target WAS instance is uninstalled completely, and then reinstalled with an updated/fixed 'maintenance.xml' file. The file must be placed into the directory 'WAS/was.primary.pak' within the WAS installation image directory.

The file can be downloaded from this IBM page: http://www-01.ibm.com/support/docview.wss?rs=180&uid=swg21268993. Detailed instructions can also be found on this page.