I found this report on this page: http://www.richinstyle.com/bugs/ie5.html

But no possible fix was listed.

Margin-left and margin-right
Bug 4: auto treated as 0
If you set margins to auto, they are replaced with 0, which is wrong when both margin-left and margin-right are auto or when either margin-left ormargin-right is set to auto and width is set to a value other than auto, or when margin-right isnot 0 and margin-left is auto.
Now what I've done in my code is this:

border-left:1px solid #ccc;
border-right:1px solid #ccc;
background:url('../images/grey-line-background.gif') repeat-y;}
How can I make the container center on the page in IE 5 and 5.5?