BGP announcements 'stuck' in route-reflector

I think this may be re-hash, apologies if so. Several people have told me Cisco IOS 'used' to have a well-known bug related to route-reflectors (clients), where they would ignore BGP withdraw messages and continue to announce routes (including full original AS path). I can duplicate this type of problem with one upstream provider (but not the other), I am trying to help them help me (as they seem to be somewhat at a stand-still resolving the problem). So far I've only gotten somewhat vague information, and haven't been able to find anything specific myself. Any pointers (Cisco bug ID, IOS releases with the problem and those that fixed it, etc) would be helpful. Thanks. Pete.