Facebook made changes this month. You have two choices.
1) Wait for boonex to update there version of facebook connect. Which when they do you would have to manually update via the SVN I have checked your site. Even tho you are using my button which you most likley got from a forum post here. You actually using the boonex version.
OR
2) Switch to a more reliable facebook connect that keeps up to date with all facebook changes. Such as mine. http://www.boonex.com/m/Deanos_Facebook_Connect_Version_2_0
Weird thing is not everyone is affected yet. Reports seem to be coming in rather slowly. So i think facebook is taking their time pushing these changes through developer accounts.