Here are the steps on how to reproduce this bug:
Normal behavior

1. Create a Test page in any space
2. In Rich Text mode, put in some contents in the page like:

   test 1
   test 2
   bla bla
   meh meh
   

3. Clicking on any part of the content and pressing the 'Delete' key works alright in any browser

Undesired behavior

1. Using any IE browser (6/7/8), with the same page in Rich Text mode, click on Wiki Markup mode and then click back to Rich Text mode
2. There will be a space in between those content:

   test 1
   
   test 2
   
   bla bla
   
   meh meh
   

3. Clicking between the space and press on the 'Delete' key (it just hangs there without any response)
4. In Firefox, there is no space in between the content and pressing on the 'Delete' key works fine

Besides, clicking on in between the words and pressing on 'Delete' key works fine in any IE browser. However, typing any new words and then click your mouse cursor below the word, you will see that the cursor will go down when you press on the 'Delete' key.

This behavior is seen in Confluence 2.10.3 and Confluence 3.2.x.