Just to report that after the upgrade I had so far only 2 crashes in Plasma.
Still not the desirable behavior but improving. I'll keep this thread open and perhaps wait for Qt 4.8.5.

The patch in slackware-current fixed my Plasma crashes on the ARM Chromebook when I recompiled the ARM package with it. Recompiling qt4 with "-Os" did not fix that crash.

Eric

Today I had more 4 crashes. This is may .xsession-errors (partial):

file:///usr/share/apps/plasma/plasmoids/org.kde.notifications/contents/ui/LastNotificationPopup.qml:222:17: QML QDeclarativeItem_QML_110: Foi detectado um ciclo de associações para a propriedade "tallText"
CLIENT: Task: Task::done()
CLIENT: Task: emitting finished
plasmapackage:/ui/NotificationDelegate/NotificationDelegate.qml:189:21: QML TextEdit: Foi detectado um ciclo de âncoras no método 'fill'.
plasmapackage:/ui/NotificationDelegate/NotificationDelegate.qml:143:13: QML Item: Foi detectado um ciclo de associações para a propriedade "height"
plasmapackage:/ui/NotificationDelegate/NotificationDelegate.qml:143:13: QML Item: Foi detectado um ciclo de associações para a propriedade "height"
plasmapackage:/ui/NotificationDelegate/NotificationDelegate.qml:143:13: QML Item: Foi detectado um ciclo de associações para a propriedade "height"
KCrash: Attempting to start /usr/bin/plasma-desktop from kdeinit
KCrash: Application 'plasma-desktop' crashing...
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
QDBusObjectPath: invalid path ""
This is the current thread id for Activities 139656322270976 QThread(0x24f0700)
plasma-desktop(20170)/libplasma Plasma::isPluginVersionCompatible: unversioned plugin detected, may result in instability

Ok and for those non-portuguese speakers, the three first portuguese phrases mean, respectively:
It was detected an association cycle for property "tallText";
It was detected an anchor cycle in method 'fill'; and
It was detected an association cycle for property "height".

Thanks.

After Apr 29th updates, I didn't experience any more crashes, so I'll close this thread as solved.
Thank you guys for your support.
Have a wonderful week.