I have a new build out of Exchange 2010 sp1 with CAS, Hub and Mailbox on one physical server (no other roles).
When trying to add another CAS on Hyper-V, the installation failed and I had to start from scratch because I wasn't able to uninstall (had to remove from AD/Schema and reset the account).
Having all of the pre-reqs AFAIK, I get the following error:
Client Access Server Role FAILED
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 1168.".
The Exchange Server setup operation didn't complete. More details can be found in ExchangeSetup.log located in the <SystemDrive>:\ExchangeSetupLogs folder.
Exchange Server setup encountered an error.