Pasting plain text

I am trying to paste plain text into CKEditor with IE8, and I am encountering a strange problem:

The CKEditor begins with the following text:

four

five

(the first line is blank)

I then copy and paste the following text from Windows Notepad (so I know it's plain text) into CKEditor starting at the first line (the blank line):

one

two

three

(Three lines with a blank line in between each)

The resulting text in CKEditor after the paste is as follows:

one

four

five

two
three

I would have expected this:

one

two

three

four

five

Has anyone else seen this problem and, if so, do you know a solution? Thanks!

Note: I can reproduce this problem on the CKEditor demo page here: http://ckeditor.com/demo
The problem only occurs with Internet Explorer, and does not occur with Firefox.