Comment # 4 on bug 900849 from Bernhard Wiedemann

I found an interesting reproducer:

LANG=foo kdesu -c 'xterm'

would come up with a console and doing in there echo $LANG
would give the expected result of 'foo'.

LANG=bar kdesu -c 'xterm'
echo $LANG

however would return foo instead of bar, 
even after a killall kdesud,
so probably not related to the caching of passwords