Exchange 2010 Reinstall CAS role error

Summary: 3 item(s). 1 succeeded, 1 failed.
Elapsed time: 00:00:09

Preparing Setup
Completed
Elapsed Time: 00:00:07

Client Access Role
Failed
Error:
The following error was generated when "$error.Clear();
          $CommandAppCmd = join-path $env:SystemRoot System32\inetsrv\appcmd.exe;
          $imagePath = [System.IO.Path]::Combine($RoleInstallPath, "ClientAccess\Owa\auth\exppw.dll");
          Start-SetupProcess -Name "$CommandAppCmd" -args "install module /name:exppw /image:`"$imagePath`" /add:false" -IgnoreExitCode @(183);
          Start-SetupProcess -Name "$CommandAppCmd" -args "add module /name:exppw /app.name:`"Default Web Site/owa`"" -IgnoreExitCode @(183);
        " was run: "Process execution failed with exit code 50.".
Process execution failed with exit code 50.
Click here for help... http://technet.microsoft.com/en-US/library/ms.exch.err.default(EXCHG.141).aspx?v=14.1.267.0&e=ms.exch.err.Ex88D115&l=0&cl=cp
Elapsed Time: 00:00:02

Finalizing Setup
Cancelled
 
 
Please advise