Outlook 2010 – Contact Groups not visible on the ‘TO’ button

Just upgraded to Office 2010 and am finding that the changes from 2007 are confusing.
When composing a new email, in 2007 when I pressed the ‘to’ button I could see my contact list including any Groups; in 2010 all I see is the full list of individual contacts.
Very retrograde step but I’m sure there must be a way round.
I rely on you chaps/chapesses out there, please