The MSRT updates are cumulative "updates". (Actually it's just a scanner with a regularly updated data file.) You should decline the older MSRTs and approve/deploy only the latest update.
The updates have supersession links, but they only go back for a few months, so that would explain something as old as Oct 2010 not being excluded by the WUAgent. Most likely the April, May and June MSRTs are being ignored.
Thank you Lawrence. I appreciate the prompt reply. That makes sense to me so I will give that a try.