Using the Search Major Giving Prospect from the Prospect functional area returns the prospect plan information for any prospect entered into the search. However it is also including the Primary plan manager from plans that are marked Historical.
We're currently evaluating this issue for a fix in a future patch or service pack.
Steps to Duplicate
Select a constituent with the Major Giving Prospect constituency (or add it)
Go to the Prospects tab of the constituent record
Select the Plans sub-tab
Select Add major giving plan
Enter the following:
Repeat steps 4-7 adding a second plan with a different Primary manger
Make one of the plans historical
Go to the Prospects functional area
Select Search Major Giving Prospects
Enter the name of the constituent from above
Observe the results list displays the Primary plan mangers for both the active and historical plans