Q. What does the error message "a MIB counter has wrapped" mean?
A. InterMapper computes utilization by measuring the rate of change of the ifInOctets and ifOutOctets counters. These counters increase by one for every byte received or transmitted.
The message saying that "a MIB counter has wrapped" indicates that the measured value of a counter was less than the previous measured value. This can occur if the counter has been reset to 0 due to some change in the device or link.
If the message continues to exist, try to change SNMPv1 to SNMPv2. SNMPv2 supports larger counter values. Make sure the map is open for edit mode, right-click the device and choose Set Info > Set Probe to access the set probe dialog and set the SNMP version in the drop-down box there. If the warning hasn't cleared on its own, try selecting the device and choosing 'reprobe selection' from the context menu.
Even when the MIB counter wraps, InterMapper still shows the value it computed. The asterisk is a footnote explaining that the value may or may not be legitimate. (It's possible for a counter to legitimately wrap, and still yield useful information).