Hi, Bastien, 

Here is a recipe for what might be another manifestation
of this bug.

I'm using the maint branch: Org-mode version 8.2.6
(release_8.2.6-21-g3b9419 @ /src/org-mode/lisp/).

Files `setup.el' and `test-case.org' are attached.
The directory added to the load path in `setup.el'
will probably need to be customized.

Steps:

1. Run Emacs: `emacs -Q -l setup.el'.

2. Open the agenda: `M-x org-agenda RET a'.

3. Add a tag filter: `/ TAB foo RET'.

4. Move point to the agenda line containing the TODO item:
`C-s TODO RET'.

5. Move point to the end of the line with `C-e'.
It does apparently move to the end of the line.
However, `C-x =' reports that it is in column 0.
I expected it to be in column 108 or 109.

6. Try to move point to the beginning of the line with `C-a'.
It appears to move one column to the left.  I expected it
to move to the left edge of the window.  `C-x =' says it is
in column 108.

7. Try again to move to the beginning of line with `C-a'.
This works.

8. Clock in with `I'.  Parts of the line change color
but in column 0 `C-u C-x =' does not list any face.
I expected the whole line to be highlighted with face
`org-agenda-clocking'.

9. Now try to go to the item in the source Org file: `TAB'.
I see this error: `Command not allowed in this line'.

Best,
Thomas