Theme or plugin conflict. Have you tried deactivating plugins except BuddyPress to check which one is messing up with your widgets?
Cheers. I have tried this previously with no luck.
A previous post on BuddyPress suggests it may be an error with the jQuery easing plugin as part of the BP framework:
http://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/widgets-are-not-working-buddypress-1-5/?topic_page=2&num=15#post-109779
I’ll keep an eye on further responses for now.
Thanks again mercime