A bug was introduced in autoupdate package #5 (AU5) that led to the symptoms you reported. There were many changes made to the traffic data collector in AU5, almost all related to improving collection scalability. Normally changes of this magnitude would not be included in an autoupdate but it was felt that the potential benefits in terms of scalability were worth the heightened risk, as the code had been under test within the development lab for about 6 weeks prior to the release of AU5.
In a nutshell, our testing failed to anticipate a particular pattern of IP addressing which anyone who has seen this bug has in their environment. When the collector receives sFlow samples from devices that meet the pattern it gets confused when computing hash keys from the incoming sFlow datagrams, and essentially multiplexes the data from multiple ports (across the devices) into the same set of internal data counters. This multiplexing leads to the erroneous values you observed in Traffic Monitor. Note that *only* sFlow data collection is affected by this bug - AU5 will correctly report statistics and sampled XRMON data.
This problem has been remedied and another autoupdate that fixes the problem, AU6, is on the way this week. We are truly sorry for any issues that this bug has caused for you. Please rest assured that we have augmented our testing procedures to ensure that nothing of this sort will occur again, and that changes proposed for inclusion in autoupdate will undergo additional scrutiny before they are accepted from this point forward.
Regards,
SVB