Found the cause of the problem! Looks like a bug!
In /wp/wp-admin/wp-admin.css line 1879 :
.js .theEditor {
color: white;
}
This causes the text in the Editor to be white on a white background. Change the color to ‘black’ or whatever you want.
The problem did not occur in our previous installation because there was no such entry in the wp-admin.css in WP 2.7.x
wobo