Xcode Code signing error, try to resolve 'too few items in teams'

HI ,

I've been developing apps for a few weeks in Xcode 4, building and running without problems. Today when I try to build anything

I get 'The identity 'iPhone developer' doesn't match any valid, non expected certificate/privilege key pair in your keychains '

The only solution i tried was to go to the Xcode Organizer window/ Devices tab / Provisioning profiles . This displayed a blank

page . I try 'Refresh' (icon in bottom right corner) and I get another message ' Too few items in teams' !

(the only change i made today in Xcode is to try and connect to a svn repository...and failed )

thanks in advance