Comment 4 for bug 51421

I can confirm this bug as well. I'm unsure if the problem is actually related to 'gtk2-engines-gtk-qt' but it seems to originate from applications using GTK toolkit running in KDE.

At times (apparently when changing color settings, etc. in 'kcontrol'), applications like 'Firefox' or 'streamtuner' freeze for well over 10 sec causing the 'Xorg' process to allocate more and more memory. Once GTK-based applications start responding, memory usage stops increasing. Closing the applications in question doesn't deallocate memory. Eventually, memory usage grows out of control, slows down the entire system and the only solution is to restart X.