Hello,
I'm pretty new to Qt, Python and their combinations. I'm currently writing a QGIS plugin in python (I used QtCreator 2.1 (Qt Designer 4.7) to generate a .ui-file and am now trying to use it for a Quantum GIS plugin that's written in Python 2.5 (and running in the Quantum GIS Python 2.5 console)). 
I am running into trouble when loading the ui-file dynamically when the program runs the loadUi() function. What throws me off is that the error occurs outside my script. Does that mean, I'm passing something wrong into it? Where does the error come in? Any hints on what could be wrong? 
code_dir = os.path.dirname(os.path.abspath(__file__)) 
self.ui = loadUi(os.path.join(code_dir, "Ui_myfile.ui"), self)
This is the Error Code I am getting (minus the first paragraph):
File "C:/Dokumente und Einstellungen/name.name/.qgis/python/plugins\myfile\myfile_gui.py", line 42, in __ init __
self.ui = loadUi(os.path.join(code_dir, "Ui_myfile.ui"), self)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic__init__.py", line 112, in loadUi
 return DynamicUILoader().loadUi(uifile, baseinstance)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic\Loader\loader.py", line 21, in loadUi
 return self.parse(filename)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic\uiparser.py", line 768, in parse
 actor(elem)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic\uiparser.py", line 616, in createUserInterface
 self.traverseWidgetTree(elem)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic\uiparser.py", line 594, in traverseWidgetTree
 handler(self, child)
File "C:\PROGRA~1\QUANTU~1\apps\Python25\lib\site-packages\PyQt4\uic\uiparser.py", line 233, in createWidget
 topwidget.setCentralWidget(widget)
SystemError: error return without exception set