X desktop doesn't load after OS9


I have repeated this several times now.

After installing OSX and then rebooting into 9 to run some programs and then going back to X, when it is time for the desktop to appear everything just stalls. there is no hope to get back in except the ultimate cure... reinstall both 9 and 10 after an HD reformat. Then it all works again.

Does anyone know what's up with this insane problem?