Well I've tried multiple times to use the portal in the pocket dimension after correctly entering a code I got from graffiti, but it always gives the sound effect, with the game screen just frozen, and a few moments later the game crashes.
Try with the latest hotfix: http://patches.gaslampgames.com/dredmor/dredmor_hotfix_final_v5.zip or wait for the patch to hit distributors which should be quite soon.