kontact crashes from time to time

From time to time when I switch in kontact from one view to the contacts view, kontact crashes. Now I looked into .xsession-err *** Error in `kontact': malloc(): memory corruption (fast): 0x0000000002291eeb *** [TDE NM Backend ERROR] [/opt/software_x64/KDE/TDE/tdelibs/tdecore/tdehw/networkbackends/network-manager/network-manager.cpp:1823] Attempting to access the network-manager VPN service returned: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.NetworkManager.VPN.Plugin was not provided by any .service files WeaverThreadLogger: thread (ID: 2) suspended. WeaverThreadLogger: thread (ID: 4) suspended. WeaverThreadLogger: thread (ID: 3) suspended. WeaverThreadLogger: thread (ID: 1) suspended. *** KMail got signal 6 (Crashing) How can I track this down? Should I turn on debugging for all that ... and what partiularly thanks regards