Can you give more information about the OS you are installing the PowerCLI on? What version of PowerCLI are you trying to install?
It sound like a .net framework issue. Are you running the installer as "Run as Administrator"? try that and see if it resolves.
Try this solution.
From Microsoft community.
Hit the same issue!
Looks more like an error with the .NET framework. I uninstalled it (from Control Panel -> Programs) & re-installed using the 'Turn Windows features on or off' - Full installation of Windows .NET framework -> Reboot -> Tried initiating the PowerCLI installation again & it worked.
Hope it works for you too!
~Sharat