Trying to understand MDT2012 Multi-Cast

I'm trying to use MDT 2012 from Server 2008R2 to image about 50 computers (volunteering at kids school)

CONFIGURATION

Server 2008R2

MDT 2012 integrated with WDS

Clients are Windows 7

HP Procurve V1910-48 Gigabit Switch with IGMP Level 3 Snooping enabled (and no multi-cast broadcast limits)

Everything works wonderfully when Uni-casting the images to the PC's but, when you unicast 50 PC's the time to image all 50 is roughly 2 hours.

We enabled the share for Multi-Casting in MDT

and WDS shows Multicast Transmissions -> MDT Share Deployment$  when you right mouse click properties it shows Autocast and Active

But, no sessions show up in WDS.

In the event log on the server there are 2 error messages for each connection

First error

 

Source:        WDSServer
Date:          7/17/2013 5:16:56 PM
Event ID:      772
Task Category: WDSServer
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      OURSERVER
Description:
An error occurred while trying to create the UDP endpoint for WDSMC provider on interface 192.168.151.17:64943. This can happen if the network interface was disabled or changed, or some other application is already using the port. The provider  will not be able to receive requests on this interface. 

 Error Information: 0x2 

Second Error

Source:        WDSServer

Date:          7/17/2013 5:16:56 PM
Event ID:      1539
Task Category: WDSServer
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      OURSERVER
Description:
There are no available MADCAP servers on interface 192.168.151.17. 

I'm not sure where to go next to troubleshoot / resolve this issue.

Any Pointers???