I have DTEXT in a title block. I edit the text and it disappears. Regen gets it back but you cannot do anything with the text afterward.
Change the TEXTED system variable to 1. This changes the editor to the old style editor. Wait for a service pack to fix this bug.
Run AUDIT on the drawing.
If the TEXTED variable is already set to 1 an AUDIT seemed to correct the problem if it persists.