blackbox vs. gimp layer masks

[Vincent Kraeutler]

I have been experiencing a serious problem when trying to use 
gimp layer masks with blackbox.
In order to edit them, one needs to Mod1-Click on the little 
layer mask icon in the layers dialog, which, in blackbox,
simply causes the window to be dragged around...
any suggestions?
I have been very happy wit BB so far and would only
reluctantly return to sawfish/gnome.

vincent