I found that adding certain characters to the front of the text in a drawn
Ellipse will cause the text to disappear.  

This is found in OOo 2.2.1 and 2.3.1

Computer: HP PC Desktop and MDG Laptop
OS: Windows XP Service Pack 2

Here are some instructions to replicate the issue.

1. Open Draw
2. Select Ellipse drawing tool by mouse, located bottom left toolbar.
3. Draw Ellipse by mouse on blank drawing.
4. Double-click on drawn Ellipse to enter text edit mode.
5. Type the number 1.
6. Press left arrow key to put cursor at the front of the 1.
7. Type the number 0. (The text in the Ellipse disappears).
8. Press left arrow key again to put cursor at front of text.
9. Type the number 0. (The text in the Ellipse reappears).

In fact the text will disappear if a 0 is put in front of the following text:

1
0001
000001
00000001

or place 'a' in front of 'aaaa'.

The additional character is there, it appears if you click on the Ellipse, it is
disappearing during the editing of the text.

This behavior also appears with the Rectangle drawing tool.

Also copied the Ellipse and pasted into a blank Writer document.  This Ellipse
did not exhibit the disappearing behavour.