When installing Powershell v3, it doesn't install any local help files for get-help. If you are upgrading from v2 to v3, the help isn't updated either.
If you are using a proxy, a simple update-help may not work for you.
Do the following:
$webclient = New-Object System.Net.WebClient
$creds = Get-Credential
$webclient.Proxy.Credentials = $creds
This will connect to the internet and download the updated help files.