Results of the day:
1) The external monitor plays nothing here: I've booted the live Jaunty VGA disconnected, switched to UXA; same symptoms.
2) The leak seems related to the screen resolution i.e. 1920×1200 window open/close fills my memory quicker than with 1280×800 screen.
I'm now going to report this upstream as suggested.
Results of the day:
1) The external monitor plays nothing here:
I've booted the live Jaunty VGA disconnected, switched to UXA; same symptoms.
2) The leak seems related to the screen resolution i.e. 1920×1200 window open/close fills my memory quicker than with 1280×800 screen.
I'm now going to report this upstream as suggested.