Version:            (using Devel)
Installed from:    Compiled sources
OS:                Linux

I am running KDE from SVN trunk. (kdeplasmoids was checked out less than an hour ago, the rest is a day or two old.)

Steps to Reproduce:
1. Add Widgets
2. Place a Notes applet on the background
3. Hover to handle, select configure, and enable spell-checking.
4. Click on the note to enable editing: the word "Plasmoid" will become highlighted in red.
5. Hover to the handle, and click the X to delete the applet

Results:
Plasma crashes.

Reproducibility:
Always. (Also occurs if a different word becomes highlighted or no word at all. The editing window does not appear to need to be active (i.e. no text caret), but if one simply enables spell-checking and closes the applet, skipping step 4, the applet exits cleanly.)

Backtrace:
Application: Plasma Workspace (<unknown>), signal SIGSEGV
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1208703280 (LWP 7036)]
[New Thread -1249113200 (LWP 7045)]
[New Thread -1233437808 (LWP 7037)]
[KCrash handler]
#6  0x06f78b15 in QTextEdit::document ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#7  0x01572835 in QTextEdit::toPlainText (this=0x0)
    at /home/kde4/qt-copy/include/QtGui/qtextedit.h:192
#8  0x0156fb7c in Notes::saveNote (this=0x8d1a318)
    at /home/kde4/kde/src/KDE/kdeplasmoids/applets/notes/notes.cpp:125
#9  0x0157018e in Notes::qt_metacall (this=0x8d1a318, 
    _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0xbf972378)
    at /home/kde4/kde/build/KDE/kdeplasmoids/applets/notes/notes.moc:71
#10 0x01b898a1 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#11 0x01b89f32 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#12 0x06f77107 in QTextEdit::textChanged ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#13 0x06f7cf87 in QTextEdit::qt_metacall ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#14 0x0127582a in KTextEdit::qt_metacall (this=0x8d1aa00, 
    _c=QMetaObject::InvokeMetaMethod, _id=31, _a=0xbf9724b8)
    at /home/kde4/kde/build/KDE/kdelibs/kdeui/ktextedit.moc:96
#15 0x01b898a1 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#16 0x01b89f32 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#17 0x06d53567 in QTextControl::textChanged ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#18 0x06d5d317 in QTextControl::qt_metacall ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#19 0x01b898a1 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#20 0x01b89f32 in QMetaObject::activate ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#21 0x07153887 in QTextDocument::contentsChanged ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#22 0x06d8d5ce in ?? () from /home/kde4/qt-copy/lib/libQtGui.so.4
#23 0x06d8f747 in ?? () from /home/kde4/qt-copy/lib/libQtGui.so.4
#24 0x06db48b0 in QTextCursor::endEditBlock ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#25 0x06dc8700 in QSyntaxHighlighter::setDocument ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#26 0x06dc88a8 in QSyntaxHighlighter::~QSyntaxHighlighter$base ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#27 0x011e9737 in ~Highlighter (this=0x8e1bbf0)
    at /home/kde4/kde/src/KDE/kdelibs/kdeui/sonnet/highlighter.cpp:127
#28 0x01275bc5 in ~Private (this=0x8d20218)
    at /home/kde4/kde/src/KDE/kdelibs/kdeui/widgets/ktextedit.cpp:61
#29 0x0127519c in ~KTextEdit (this=0x8d1aa00)
    at /home/kde4/kde/src/KDE/kdelibs/kdeui/widgets/ktextedit.cpp:219
#30 0x0713861e in QGraphicsProxyWidget::~QGraphicsProxyWidget$base ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#31 0x00312fc8 in ~TextEdit (this=0x8bfa148)
    at /home/kde4/kde/src/KDE/kdebase/workspace/libs/plasma/widgets/textedit.cpp:58
#32 0x015704f9 in ~Notes (this=0x8d1a318)
    at /home/kde4/kde/src/KDE/kdeplasmoids/applets/notes/notes.cpp:67
#33 0x01b8329c in qDeleteInEventHandler ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#34 0x01b84fb3 in QObject::event () from /home/kde4/qt-copy/lib/libQtCore.so.4
#35 0x07127823 in QGraphicsWidget::event ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#36 0x06b7206f in QApplicationPrivate::notify_helper ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#37 0x06b76d29 in QApplication::notify ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#38 0x0118c553 in KApplication::notify (this=0x868c640, receiver=0x8d1a318, 
    event=0x8e5c9e8)
    at /home/kde4/kde/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:311
#39 0x01b748f9 in QCoreApplication::notifyInternal ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#40 0x01b7597e in QCoreApplicationPrivate::sendPostedEvents ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#41 0x01b75c2d in QCoreApplication::sendPostedEvents ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#42 0x01b9facf in ?? () from /home/kde4/qt-copy/lib/libQtCore.so.4
#43 0x03ff61ac in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#44 0x03ff95ef in ?? () from /lib/libglib-2.0.so.0
#45 0x03ff9b55 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#46 0x01b9fe7e in QEventDispatcherGlib::processEvents ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#47 0x06c02bc5 in ?? () from /home/kde4/qt-copy/lib/libQtGui.so.4
#48 0x01b73b8d in QEventLoop::processEvents ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#49 0x01b73d1d in QEventLoop::exec ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#50 0x01b75ced in QCoreApplication::exec ()
   from /home/kde4/qt-copy/lib/libQtCore.so.4
#51 0x06b71a27 in QApplication::exec ()
   from /home/kde4/qt-copy/lib/libQtGui.so.4
#52 0x00123d26 in kdemain (argc=2, argv=0xbf973134)
    at /home/kde4/kde/src/KDE/kdebase/workspace/plasma/plasma/main.cpp:54
#53 0x08048812 in main (argc=)
    at /home/kde4/kde/build/KDE/kdebase/workspace/plasma/plasma/plasma-qgv_dummy.cpp:3
#0  0x00110416 in __kernel_vsyscall ()