I can see it also sometimes, but I use experimental packages of debian and I guess it's related.
It never happened to me with KDE, only on gnome.
It seems to be a deadlock in thread-handling, because the processes remain in status "futex_wait_queue_me" (seen with gnomes process-monitor).
At the moment it does not happen (as far as I see).
wxWidgets 2.8.10
libgtk2.0 2.23.3
libglib2.0 2.27.5
As far as I remember it does only happen if codecompletion- and compiler-plugin are enabled. If one of them is disabled it does not happen.
If build with wxWidgets debug-version, it tells me, that 4 threads are not terminated by C::B itself, and that wxWidgets has to kill them.
The four threads are the FileManager background threads (fileLoaderThread, uncLoaderThread, urlLoaderThread, delayedDeleteThread) and this is most likely not related to the deadlock.