I have a trouble with org-columns-edit-value; updating property using
this command breaks property formatting.

If I update MyProp_B in,

   :PROPERTIES:
   :MyProp_A: a
   :MyProp_B: b
   :END:

I end up with:

   :PROPERTIES:
   :MyProp_A: :MyProp_B: x a

   :END:


I found that (match-beginning 0) returns different value after
(delete-region (match-beginning 0) (match-end 0)).  The strange thing
is that I could not reproduce it in "plain" Emacs without loading my
init.el.

I am using a few week older version from Emacs trunk.
emacs-version: "24.2.50.1"
emacs-bzr-version: "110740 rgm@gnu.org-20121030101856-aimepc487hfjuqqs"


I will try to reproduce the bug after updating Emacs (probably to the
24.3 release branch) and org-mode later.  But I thought I'd share the
patch first.