I used to get the same problem.
When you're setting up MDK, set your video resolution really low (I - for instance - had to set my video settings to 1152x768-24bit). I don't have the world's greatest video card, but it works fine. From there, I just set up the resolution higher, until I got to a resolution I liked. If your resolution is too high for your video card, you'll get that black screen.
You don't need to re-install MDK when this happens: just load in the Install DVD, and skip to the last screen (the Summary screen), and re-set your video settings from there.
PS. MDK 2006.0's installer features a developmental(ly challenged) version of X.org. As soon as you get into a desktop/window manager, bring up MCC (Mandriva Control Centre) and run the updates. I just re-installed about a week ago, and I was looking at about 50MB - 200MB worth of updates.
PPS. Just a side note, don't use the version of WINE that comes with MDK - go to http://www.winehq.org
and download the RPM they have in the downloads section. The MDK version of WINE presents hardware access issues with some windows software (ie. DVD Shrink).