got trouble while uninstalling ussd-widget
then looked "Details" (in "unable to uninstall" popup)
there was two packages wich depended on ussd-widget: fAPN and pygtkeditor,
dunno why
removed dependent packages (m.b. you have another list of them) and ussd-widget uninstalled successfully
m.b strange dependencies are case of all this troubles with updating|instaling|uninstalling of ussd-widget

excuse me for my poor English