I installed kdesdk4 package using macports. I can start other apps in this package, but not umbrello. I also downloaded last unstable version from git, and the exact same situation occurs. I think this could be related to an external dependency, but I don't have enough knowledge about umbrello and kde to carry an investigation.

Reproducible: Always

Steps to Reproduce:
1. port install kdesdk4
2. cd /Applications/MacPorts/KDE4/umbrello.app/Contents/MacOS
3. ./umbrello
Actual Results:  
This is the terminal output:
umbrello(3332)/KSharedDataCache ensureFileAllocated: This system misses support for posix_fallocate() -- ensure this partition has room for at least 10547296 bytes.
umbrello(3332)/kdeui (kdelibs): Attempt to use QAction "edit_undo" with KXMLGUIFactory!
umbrello(3332)/kdeui (kdelibs): Attempt to use QAction "edit_redo" with KXMLGUIFactory!
umbrello(3332) UMLApp::setCurrentView: view is NULL
umbrello(3332) UMLApp::setCurrentView: view is NULL
umbrello(3332) *UMLDoc::createDiagram: folder= "Logical View"  / type= "Class"  / name= "class diagram"
umbrello(3332) UMLDoc::addView: "class diagram"  to folder  UMLFolder: localName="Logical View", folderFile="", diagrams=0
umbrello(3332) UMLDoc::changeCurrentView: id= "4QQ0CrKAqgkU"
Segmentation fault

If I attach gdb, I get this bt:
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: 13 at address: 0x0000000000000000
0x00000001010c30b9 in KTabWidget::Private::updateTab ()
(gdb) bt
#0  0x00000001010c30b9 in KTabWidget::Private::updateTab ()
#1  0x00000001010c342a in KTabWidget::Private::resizeTabs ()
#2  0x0000000101c34ebb in QWidget::event ()
#3  0x000000010201d6b8 in QTabWidget::event ()
#4  0x0000000101bdd4ad in QApplicationPrivate::notify_helper ()

Expected Results:  
Start fine.

./umbrello --version
Qt: 4.8.4
KDE Development Platform: 4.10.3
Umbrello UML Modeller: 2.10.3

g++ -v
Using built-in specs.
Target: i686-apple-darwin10
Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2336.1~3/src/configure --disable-checking --enable-werror --prefix=/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin10 --enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.1~3/dst-llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin10- --host=x86_64-apple-darwin10 --target=i686-apple-darwin10 --with-gxx-include-dir=/usr/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00)