Problem:
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.
Solution:
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.