Did you ever have the 1.33 patch installed, and maybe ran into the black map bug?
Long shot, but try deleting all of the files in the '
..\Divine Divinity\Run\Dynamic' folder.
This folder is used as a cache for the game. Files are created / copied there from the save game folder when you load, and written / copied from that folder when you save a game. The files will be re-created as required the next time you start Divinity. If there was a corrupt file in that folder, deleting the files should fix the problem.
Then if you have a recent save just before reading the parchment, try that, otherwise just try again with your latest save.
The lower levels are optional, but you can get past the stairs with;
Teleporting Anywhere, via hex editorcoordinates:
X = 40 6F ;
Y = 70 D9 ;
map = 00 - Iona's dungeon, level 2, at the stairs from level 1
