Obviously, the second digit is cut just as anything out of a <div>
whose style is set as {overflow: hidden}
So 1x is shown as 1, x is hidden, or overwritten by next element.
If your book shows correctly on Nook and ADE,
That means it may be a bug of the reader app on Nook Color.
To solve this problem, you can change the ordered list into
plain paragraphs leading with real numbers.
MS Word can save ordered list as HTML in different forms,
In Word 2007 up, it will be saved as <ol> in html
in Word 200-2003, it will be saved as <p>x. in html