MacOS – Powerpoint 2011 – Selection of Shapes does not work anymore

I have a totally weird problem here and I am close to tears, because that strange bug is in heavy conflict with my timeline :/.

My Problem:

• I click on a shape (no problem with images).
• the shape is displayed as selected with resize handlers etc. (the edit shape mode in light blue, not the edit text mode in light grey).
• But I can't copy or delete the shape. CMD+C or DEL don't trigger any reactions (normally the menu flickers briefly to indicate that shortcut worked).

My guess is that it is a problem with the selection mechanism, because:

• When I select a shape by encircling it with the selection marker (click mouse, keep the button down, draw the selection mask over the shape) CMD+C or DEL are working.
• The selection of the shape is displayed as described above.
• The same applies if I click on the shape and drag it around. Afterwards I can use CMD+C and DEL.
• When I select the shape with a simple click and click in the menu on "Edit" the selection instantly switches into the text edit mode. But when I use the right mouse button (or the touchpad equivalent) I reach the context menu and can select the copy-command from there (it just costs so much time to take these workarounds).

Because of that and the fact that CMD+C works in any other program flawlessly it seems to be no shortcut issue.

The problem did occur spontaneous from one moment to the other within the same PowerPoint session.

• Macbook Pro, Mac OS 10.10, PowerPoint 2011

UPDATES:

• When I select a shape with one click and then press the ESC key I can
  use the CMD+C, DEL etc. normally.
• The arrow key are affected as well: I click on a shape and press an arrow key to move it, but it does not move. Instead the shape switches into textedit mode (I get a I-Beam Cursor).