Since few days (maybe since mid-Nov 2015) my KDE display shows strange behaviours. With some menus, the items don't show, I can only read them if I hover the mouse over them. The characters are very ugly and bold. But this occurs only with menus like the system menu or some menus like those in Konsole/Kate. With other applications like Firefox or NetBeans there seems to be no problem.
I'm currently running on Kubuntu 12.04.5 LTS.
The kernel is 3.2.0-61 generic on a x86-64 (Quad core I7).
KDE version is 4.8.5
My video setup is a GeForce GTS 450 with NVidia driver 304.131.
Notice that I apply the updates as soon as they are available.
I would like to know what happens because it is very anoying. I tried to erase the .kde folder but nothing changed... I don't suspect my video board because the problem occurs only with some menus. I rather suspect KDE...??????
Do you have an idea to solve my problem?