If your system crashes when you want to run OpenCards, try starting it from xterm like this:
env SAL_NO_XINITTHREADS=true ooffice -impress.
This certainly fixed my problems. Now I can switch to Linux on my Netbook. Turns out Openoffice runs much faster in Linux than in Windows.
By the way:If you can't install the OpenCards Extension and see a large java error message, you probably haven't installed all necessary openoffice packages and activated Java. Try installing the meta-package "openoffice.org" and the package "sun-java6-bin".