For me just replacing the CaptureCardDefinitions.xml with one from a working copy was not enough. I only have the problem when doing a clean install.
My solution: First install MediaPortal 0.2, complete the configuration, do a uninstall followed by the install of 0.2.1
Strangely, I had similar problems until I installed the .NET framework 1.1 in addition to the 2.0, that cleared things up a bit.
which unfortunately fixed problems with your card for another user (according to a statement of dman)
United States of America