Julian:
Give "Check Notifications" a try:
http://www.scarybearsoftware.com/ppc_cn_overview.html
I won't go into any details on the software here, but suffice it to say that it checks the Notifications database and allows you to remove items. Like any software, it can be a bit dangerous if not used correctly, but as long as you look for your particular "sbnotif" issue, all should be well.
Hope it works.
AkiraXXX