First of all, this seems to be an Intel only issue as that people with an Ati chipset haven't seen this issue so far. The warning _xgeWireToEvent: Unknown extension 148, this should never happen. is flooding the .xsession logfile when the panel shows tooltips. (e.g. hovering above the Application Menu, hovering over a systray icon, etc). Nothing serious happens, but it would cause issues when people would require the .xsession logfile for debug. Reproducible: Always
It looks like it is about upstream : Problem caused because of libXext Patch accepted from upstream : http://patchwork.freedesktop.org/patch/22124/
I'm still suffering this bug. Has the patch been already introduced in Plasma 5.1.1?
Applying the patch in Kubuntu 14.10 as an SRU https://bugs.launchpad.net/ubuntu/vivid/+source/libxext/+bug/1400730