Exchange Web Services PS Script worked with API 1.1 but now doesn't with either 1.2 or 2.0 preview?

Here is the code that works on my old workstation that has EWS API 1.1:

$mailbox = 'XXXX@XXX.com'

Import-Module -Name "C:\Program Files\Microsoft\Exchange\Web Services\1.2\Microsoft.Exchange.WebServices.dll"
$exchService = New-Object Microsoft.Exchange.WebServices.Data.ExchangeService
$exchService.UseDefaultCredentials = $true
$exchService.AutodiscoverUrl($mailbox)

When it hits the $exchService.AutodiscoverUrl line in my new workstation with both 1.2 and 2.0 preview API on it I get this exception.  I'm wondering if any of you have any idea why I'm getting this and help me out?

Anthony