TM search results in Studio and API differ

Hi all,
Studio 2011 offers the ability to search for a term in a file-based TM. I would like to use the API in a utility that I am writing. 
However, when I enter the same term in 
Studio and in my utility, I get different results.

The good news is that my program lists the search results that Studio provides. However, my program also reports additional ones that are not reported by 
Studio. It seems that Studio does not find all occurences.
My code looks like this (it is very similar to the sample application that comes with the SDK).
SearchSettings settings = GetSearchSettings();
This results in the following settings-object:
 
SearchResults results = _fileTm.LanguageDirection.SearchText(settings, searchText);
Any idea what could be the cause? Your feedback is much appreciated!
Henk