Multiple results being returned using search for same node
There is a join in the query that is causing multiple instances of the same node to be returned.

Edit the view and under the "Other" section click on Query settings and choose Distinct.

The description says:

"This will make the view display only distinct items. If there are multiple identical items, each will be displayed only once. You can use this to try and remove duplicates from a view, though it does not always work. Note that this can slow queries down, so use it with caution."

Here is the "Other section" in the view settings:



EDIT:

If this doesn't work then try the Views Distinct Module that Sage mentions in his comment below.