Comment 46 for bug 521818

you might want to open a separate bug on gtk2-engines-qtcurve, which has the problem.
In gtk2-engines-qtcurve-1.0.2, common/common.h:1143 we have

double min=QTC_MIN(QTC_MIN(r, g), b),
           max=QTC_MAX(QTC_MAX(r, g), b),
           delta=max - min;

if max == min then delta is 0 so when we try to divide by it later on, it crashes. adding a check, something like
if (delta == 0 )
        delta=1;

seems to cover this case where r,g and b are all equal, although i've chosen a value of 1 for delta arbitrarily, the package maintainer will know if theres a wiser fix.

I've put a 'fixed' package in the ppa below if you want to check it, it works in gnome using the qtcurve engine, i assume it'll work in kde
https://launchpad.net/~sevenmachines/+archive/release+1