Version:           1.5.71 (using KDE KDE 3.5.7)
Installed from:    Ubuntu Packages
Compiler:          gcc (GCC) 4.1.2 (Ubuntu 4.1.2-0ubuntu4) 
OS:                Linux

this crash is reproducable
i use umbrello with active language ruby
create a logic view, create some classes with attributes, one classes Name: must be exactly 2 characters long,
like "Id" or "wh" "at" "ev" "er"

create one class with one public attribute, as Type: for the attribute choose the class with the 2 characters long name
after creating the class, all dialogs closed, edit again the properties of the class,
choose attributes, choose the one attribute with the type of the 2 letters class, click properties, 
delete first character of attribute Name:
press ok --> boom

backtrace:
(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1235208496 (LWP 14336)]
[KCrash handler]
#6  0xb6ad73ea in main_arena () from /lib/tls/i686/cmov/libc.so.6
#7  0x081b50ce in AssociationWidget::calculateTextPosition ()
#8  0x081b98a1 in AssociationWidget::saveIdealTextPositions ()
#9  0x081b9db6 in UMLWidget::adjustAssocs ()
#10 0x081b9fe0 in ClassifierWidget::adjustAssocs ()
#11 0x081e23e4 in UMLWidget::updateWidget ()
#12 0x08136c57 in UMLWidget::qt_invoke ()
#13 0xb77649b8 in QObject::activate_signal (this=0x8440ed0, clist=0x8641990, 
    o=0xbfb1ff8c) at kernel/qobject.cpp:2380
#14 0xb7765330 in QObject::activate_signal (this=0x8440ed0, signal=2)
    at kernel/qobject.cpp:2325
#15 0x0812021d in UMLObject::modified ()
#16 0x08120244 in UMLObject::qt_emit ()
#17 0x0812af3b in UMLCanvasObject::qt_emit ()
#18 0x0812af9f in UMLPackage::qt_emit ()
#19 0x0812b880 in UMLClassifier::qt_emit ()
#20 0xb776498c in QObject::activate_signal (this=0x8598cc8, clist=0x86824f8, 
    o=0xbfb200cc) at kernel/qobject.cpp:2378
#21 0xb7765330 in QObject::activate_signal (this=0x8598cc8, signal=2)
    at kernel/qobject.cpp:2325
#22 0x0812021d in UMLObject::modified ()
#23 0x082aeea9 in UMLAttributeDialog::apply ()
#24 0x082af4e2 in UMLAttributeDialog::slotOk ()
#25 0xb68c7409 in KDialogBase::qt_invoke (this=0xbfb20ce4, _id=-1078850332, 
    _o=0xbfb2031c) at ./kdialogbase.moc:359
#26 0x0827afe8 in UMLAttributeDialog::qt_invoke ()
#27 0xb776488b in QObject::activate_signal (this=0x86909c0, clist=0x86b8988, 
    o=0xbfb2031c) at kernel/qobject.cpp:2356
#28 0xb7765330 in QObject::activate_signal (this=0x86909c0, signal=4)
    at kernel/qobject.cpp:2325
#29 0xb7af97c7 in QButton::clicked (this=0x86909c0)
    at .moc/debug-shared-mt/moc_qbutton.cpp:152
#30 0xb7802f30 in QButton::mouseReleaseEvent (this=0x86909c0, e=0xbfb20790)
    at widgets/qbutton.cpp:836
#31 0xb779b65d in QWidget::event (this=0x86909c0, e=0xbfb20790)
    at kernel/qwidget.cpp:4702
#32 0xb76fba60 in QApplication::internalNotify (this=0xbfb22468, 
    receiver=0x86909c0, e=0xbfb20790) at kernel/qapplication.cpp:2635
#33 0xb76fdc1e in QApplication::notify (this=0xbfb22468, receiver=0x86909c0, 
    e=0xbfb20790) at kernel/qapplication.cpp:2421
#34 0xb7ebfc32 in KApplication::notify (this=0xbfb22468, receiver=0x86909c0, 
    event=0xbfb20790)
    at /root/kdelibs/kdelibs-3.5.7/./kdecore/kapplication.cpp:550
#35 0xb768e25d in QApplication::sendSpontaneousEvent (receiver=0x86909c0, 
    event=0xbfb20790) at kernel/qapplication.h:523
#36 0xb768cec2 in QETWidget::translateMouseEvent (this=0x86909c0, 
    event=0xbfb20be8) at kernel/qapplication_x11.cpp:4303
#37 0xb768afac in QApplication::x11ProcessEvent (this=0xbfb22468, 
    event=0xbfb20be8) at kernel/qapplication_x11.cpp:3480
#38 0xb76a2180 in QEventLoop::processEvents (this=0x843dc58, flags=4)
    at kernel/qeventloop_x11.cpp:192
#39 0xb7716136 in QEventLoop::enterLoop (this=0x843dc58)
    at kernel/qeventloop.cpp:198
#40 0xb76fd587 in QApplication::enter_loop (this=0xbfb22468)
    at kernel/qapplication.cpp:2793
#41 0xb791934d in QDialog::exec (this=0xbfb20ce4) at dialogs/qdialog.cpp:432
#42 0x08122153 in UMLAttribute::showPropertiesDialog ()
#43 0x082ab8bc in ClassifierListPage::slotDoubleClick ()
#44 0x082ab99e in ClassifierListPage::slotProperties ()
#45 0x082c27cb in ClassifierListPage::qt_invoke ()
#46 0xb776488b in QObject::activate_signal (this=0x8695a08, clist=0x8631248, 
    o=0xbfb20f1c) at kernel/qobject.cpp:2356
#47 0xb7765330 in QObject::activate_signal (this=0x8695a08, signal=4)
    at kernel/qobject.cpp:2325
#48 0xb7af97c7 in QButton::clicked (this=0x8695a08)
    at .moc/debug-shared-mt/moc_qbutton.cpp:152
#49 0xb7802f30 in QButton::mouseReleaseEvent (this=0x8695a08, e=0xbfb21390)
    at widgets/qbutton.cpp:836
#50 0xb779b65d in QWidget::event (this=0x8695a08, e=0xbfb21390)
    at kernel/qwidget.cpp:4702
#51 0xb76fba60 in QApplication::internalNotify (this=0xbfb22468, 
    receiver=0x8695a08, e=0xbfb21390) at kernel/qapplication.cpp:2635
#52 0xb76fdc1e in QApplication::notify (this=0xbfb22468, receiver=0x8695a08, 
    e=0xbfb21390) at kernel/qapplication.cpp:2421
#53 0xb7ebfc32 in KApplication::notify (this=0xbfb22468, receiver=0x8695a08, 
    event=0xbfb21390)
    at /root/kdelibs/kdelibs-3.5.7/./kdecore/kapplication.cpp:550
#54 0xb768e25d in QApplication::sendSpontaneousEvent (receiver=0x8695a08, 
    event=0xbfb21390) at kernel/qapplication.h:523
#55 0xb768cec2 in QETWidget::translateMouseEvent (this=0x8695a08, 
    event=0xbfb217e8) at kernel/qapplication_x11.cpp:4303
#56 0xb768afac in QApplication::x11ProcessEvent (this=0xbfb22468, 
    event=0xbfb217e8) at kernel/qapplication_x11.cpp:3480
#57 0xb76a2180 in QEventLoop::processEvents (this=0x843dc58, flags=4)
    at kernel/qeventloop_x11.cpp:192
#58 0xb7716136 in QEventLoop::enterLoop (this=0x843dc58)
    at kernel/qeventloop.cpp:198
#59 0xb76fd587 in QApplication::enter_loop (this=0xbfb22468)
    at kernel/qapplication.cpp:2793
#60 0xb791934d in QDialog::exec (this=0x85d4370) at dialogs/qdialog.cpp:432
#61 0x081675d2 in UMLWidget::showProperties ()
#62 0x081c3a0f in UMLWidget::slotMenuSelection ()
#63 0x08114864 in ToolBarStateArrow::mouseDoubleClickWidget ()
#64 0x0812a11f in ToolBarState::mouseDoubleClick ()
#65 0xb7899e2d in QScrollView::viewportMouseDoubleClickEvent (this=0x8592c88, 
    e=0xbfb21ed0) at widgets/qscrollview.cpp:1767
#66 0xb789b4e8 in QScrollView::eventFilter (this=0x8592c88, obj=0x85930f0, 
    e=0xbfb21ed0) at widgets/qscrollview.cpp:1506
#67 0xb7763e38 in QObject::activate_filters (this=0x85930f0, e=0xbfb21ed0)
    at kernel/qobject.cpp:903
#68 0xb7763eb6 in QObject::event (this=0x85930f0, e=0xbfb21ed0)
    at kernel/qobject.cpp:735
#69 0xb779b58f in QWidget::event (this=0x85930f0, e=0xbfb21ed0)
    at kernel/qwidget.cpp:4678
#70 0xb76fba60 in QApplication::internalNotify (this=0xbfb22468, 
    receiver=0x85930f0, e=0xbfb21ed0) at kernel/qapplication.cpp:2635
#71 0xb76fdc1e in QApplication::notify (this=0xbfb22468, receiver=0x85930f0, 
    e=0xbfb21ed0) at kernel/qapplication.cpp:2421
#72 0xb7ebfc32 in KApplication::notify (this=0xbfb22468, receiver=0x85930f0, 
    event=0xbfb21ed0)
    at /root/kdelibs/kdelibs-3.5.7/./kdecore/kapplication.cpp:550
#73 0xb768e25d in QApplication::sendSpontaneousEvent (receiver=0x85930f0, 
    event=0xbfb21ed0) at kernel/qapplication.h:523
#74 0xb768cec2 in QETWidget::translateMouseEvent (this=0x85930f0, 
    event=0xbfb22328) at kernel/qapplication_x11.cpp:4303
#75 0xb768afac in QApplication::x11ProcessEvent (this=0xbfb22468, 
    event=0xbfb22328) at kernel/qapplication_x11.cpp:3480
#76 0xb76a2180 in QEventLoop::processEvents (this=0x843dc58, flags=4)
    at kernel/qeventloop_x11.cpp:192
#77 0xb7716136 in QEventLoop::enterLoop (this=0x843dc58)
    at kernel/qeventloop.cpp:198
#78 0xb7715f46 in QEventLoop::exec (this=0x843dc58)
    at kernel/qeventloop.cpp:145
#79 0xb76fd609 in QApplication::exec (this=0xbfb22468)
    at kernel/qapplication.cpp:2758
#80 0x081cd3f7 in main ()

beside this crash i enjoy using umbrello :)