I Just got around this myself.

Goto Control Panel\Default Programs and click on "Set program access and computer deafults" Goto Custom, Under Choose A default e-mail program (mine was set to Use my current e-mail program) change this to Mozilla Thunderbird, then OK (check other settings while you are here - default web browser, Mozilla Firefox etc) . . . . Now it works again. Select an image, right-click, choose Send to, Mail Reciepent and Thunderbird starts and te pitcure is attached! Hooray!