Modify Group not working in 2.7.3

Hello all,

I use the "Modify Group" Property Book to let some people change group
memberships for groups in a certain sub tree (the user objects are *not*
in that sub tree).

This worked fine until I upgraded to the latest plugins, that is
iManager Framework 2.7.3.20090509, eDirectory88 Plugins 2.7.20090417 and
some more - I don't know which one is relevant. Since this upgrade the
users get this message:

"The client does not have sufficient rights to complete the requested
operation"

It still works on another server with iManager 2.7.2 and without the
other plugin updates.

Is it a bug? Can somebody confirm this?

Thanks,
Mirko