The May update for Windows 10 appears to have caused issues with opening customized SharePoint List forms in InfoPath from the list.

From the list, if you click on Customize in InfoPath, you may get the following error:

The SOAP response indicates that an error occurred on the server:

Exception of type 'Microsoft.SharePoint.SoapServer.SoapServerException' was thrown.
<detail><errorstring xmlns="http://schemas.microsoft.com/sharepoint/soap/">
    List does not exist.
    The page you selected contains a list that does not exist.  It may have been deleted by another user.
    </errorstring><errorcode xmlns="http://schemas.microsoft.com/sharepoint/soap/%22%3E0x82000006%3C/errorcode%3E%3C/detail>

 Nice, right? Especially since you were in the list when you clicked the button, so you know full well the list exists.

Click Customize in InfoPath again from the ribbon and the form should open in design mode. Or, start from InfoPath Designer - New > SharePoint List > enter your server URL and select your list - that opened the list form on my system without an error.