[PD] pd gui: partial interface freeze

[ub at xdv.org]

hey there,

i've been having this heisenbug for some time and learned to live with 
it, but having fixed some real bugs on my patch,
this is the last one on my list and i'd like to give it a go, but no 
idea where to start.

symptoms are:
some time into performing (20min to 1h) all the sliders, messageboxes, 
dials and bangs sort of get stuck,
meaning they do not change their display state anymore. i can however 
still drag and click their active parts
and their output will react accordingly, but none of this is being 
displayed.
i should probably mention, that checkboxes still work correctly.

i had hoped it would go away moving from pd 0.42 to 0.43, but it didn't.

this is 64-bit linux (ubuntu 12.04), pd-extended (now ubuntu-package, 
previously
self compiled from git)

speculations include:
from a gut-feeling i suspect something like an input overload, ie some input
shooting messsages at an insanely high rate, so the element's message queue
(if there is such a thing) stops passing things on to the display.

i also suspect vjtools/videogrid as it messes with the interface, but 
does have a few issues,
like race conditions between thumbnail creation and thumbnail display, 
esp if there's
two of them.

hid: usb joysticks could maybe freak out and overload the interface inputs

anyway i can not see any direct connection between what i do and when it 
happens.

re-opening the patch doesn't help, only restarting pd does.

has anyone ever seen (something like) that?
any ideas about how to debug, where to look or what to try?

thanks + cheers,
ub