Plasma crashing repeatedly

[henge]

hello, if anyone can help, i'd be most grateful:

when logging in lately i get a plasma error warning window with "Unknown error. (Unable to fetch item from backend)"

Although i am then able to continue, i am getting repeated desktop crashes, seemingly related to plasma...

error log below:

Application: Plasma Desktop Shell (plasma-desktop), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f4619421780 (LWP 1599))]

Thread 4 (Thread 0x7f45f19ae700 (LWP 1628)):
#0 0x00007f4618cf7b03 in poll () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f460cea6036 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f460cea6164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f4615ec9426 in QEventDispatcherGlib:rocessEvents(QFlags<QEventLoop::ProcessEventsFlag> ) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#4 0x00007f4615e98c82 in QEventLoop:rocessEvents(QFlags<QEventLoop::ProcessEventsFlag> ) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#5 0x00007f4615e98ed7 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsF lag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#6 0x00007f4615d97fa7 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#7 0x00007f4615e789ff in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#8 0x00007f4615d9afcb in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9 0x00007f460d7aae9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#10 0x00007f4618d034bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#11 0x0000000000000000 in ?? ()

Thread 3 (Thread 0x7f45eb7c4700 (LWP 1629)):
#0 0x00007f460d7ae05d in pthread_mutex_unlock () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f460cee15d1 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f460cea602a in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f460cea6164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4 0x00007f4615ec9426 in QEventDispatcherGlib:rocessEvents(QFlags<QEventLoop::ProcessEventsFlag> ) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#5 0x00007f4615e98c82 in QEventLoop:rocessEvents(QFlags<QEventLoop::ProcessEventsFlag> ) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#6 0x00007f4615e98ed7 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsF lag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#7 0x00007f4615d97fa7 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#8 0x00007f4615e789ff in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9 0x00007f4615d9afcb in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#10 0x00007f460d7aae9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#11 0x00007f4618d034bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#12 0x0000000000000000 in ?? ()

Thread 2 (Thread 0x7f45eacde700 (LWP 1630)):
#0 0x00007f460d7aed84 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f4612c7d222 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#2 0x00007f4612c7d259 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#3 0x00007f460d7aae9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#4 0x00007f4618d034bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#5 0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f4619421780 (LWP 1599)):
[KCrash Handler]
#6 0x00007f4618c47445 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#7 0x00007f4618c4abab in abort () from /lib/x86_64-linux-gnu/libc.so.6
#8 0x00007f4614e0869d in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#9 0x00007f4614e06846 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#10 0x00007f4614e06873 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#11 0x00007f4614e069b6 in __cxa_rethrow () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#12 0x00007f4615e9916c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsF lag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#13 0x00007f4615e9df67 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#14 0x00007f461900fa13 in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_plasma-desktop.so
#15 0x00007f4618c3276d in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#16 0x0000000000400671 in _start ()

thanks.