Cannot edit global address book DL's

On Satruday 1-31-15 our hosted exchange domain was transitioned to exchange 2010, with no notification BTW. After this users were unable to send or receive email from mobile devices and desktops until the new certificate was accepted. We did this and everything seemed fine until last Friday 2-6-15 when I tried to create a new global distribution list.

I followed all the steps outlined on Comcast's web site. I created the distribution list on the Comcast Business page then went to edit the list in Outlook as required. When I make changes to the members of the list and click OK to save them Outlook goes unresponsive and I get an error which reads:

"Outlook is trying to retrieve data from the Microsoft Exchage server W14CLBCH2.W14D.comcast.net."

Outlook will remain unrespoinsive until I force close it.

Several calls to support have been placed, one had found a valid issues with our DNS registration which was fixed. Again THANKS FOR THE HEADS UP!!!

I called tech support again today and hopefully got another Tier2 ticket, but I was also referred to Microsoft customer support as if the issue is with my PC only. There are at least two other posts on this forum from people with the same issues and no apparent fixes. 

Can someone competent within Comcast please contact me to get this resolved. I rely on externally available distribution lists to support my customers and you're currently hurting my business.

Thanks.