Interesting. When we've seen this problem in the past, it's usually been with a multi-member stack, and a reload of the stack fixes the problem. The best thing to do will be to capture the CiscoView SNMP and activity tracing debug after restarting dmgtd, and re-opening this module in CiscoView. That debugging can be enabled under CiscoView > Administration > Debug Options and Display Log. But you MUST restart dmgtd first to free the cache so that a full debug log can be produced.
Then, open a TAC service request, and include that debug log. I do not have immediate access to one of these modules to do any additional testing.