Users can no longer log onto their Desktop via RWW using just their username, they must now use DomainName\username or full email address

Hello All,

I have just inherited a system that is SBS2011.  I am still getting acquainted with this system but something I havent seen before just started happening.  Users can no longer log on to their desktop via RWW just using their logon name they must now use domainname\username or their full email address.  They can initially access the RWW website just using their username and password but when they go to access their desktop it now requires domainname as well.  Please forgive my ignorance, but what am I missing here?

Thank you in advanced for any assistance,

mjkisic