Permission issues when using JQL Tricks parent() function

It is quite difficult to describe what happens here, since we do not completely understand how GreenHopper calculates the permissions. However, all that really matters is that GreenHopper requires the 'Administer Project' permission for a user to allow him to use the 'Add Sprint' button on a rapid board.

We have created a GreenHopper board and we are now trying to include sub-tasks into the filter via the following query:

(project = ABC AND reporter = user1) OR issue in parent("project = ABC AND reporter = user1") ORDER BY Rank ASC

This actually works quite well as long as the parent() function returns something. If it returns an empty set, the 'Add Sprint' button is disabled and GreenHopper complains about a missing 'Administer Project' permission. We changed the query slightly by including two reporters thus forcing the parent() function to return an empty result:

(project = ABC AND reporter = user1) OR issue in parent("project = ABC AND reporter = user1 AND reporter = user2") ORDER BY Rank ASC

Now the 'Add Sprint' button is missing even though this JQL query return exactly the same issues as if we remove the parent() function completely ((project = ABC AND reporter = user1) ORDER BY Rank ASC).

I am not sure if this is problem relates to GreenHopper or JQLT therefore I created a bug report on both ends.