had a same issue started yesterday, could not even load Cydia menu (to remove source via cydia), so ended up using ifunbox to edit sources (bad one for me was s i nf ul iphone), removed the one mentioned, then had to go and remove/edit in metadata for sources... At any rate, worked great. Readded source and like nothing ever happened. Another iphone4 did not experience the same issue at all, what gives.