I cannot help you much without a small (possibly reduced) snippit of the problem. If the problem is what I think it is then it's because a div by default takes up 100% width, and as such cannot be aligned.
What you may be after is to align the inline elements inside the div (such as text) with text-align:center; otherwise you may consider setting the div to display:inline-block;
If you do go down the inline-block route then you may have to consider my favorite IE hack.
width:100px;
display:inline-block;
zoom:1; //IE only
*display:inline; //IE only
Happy Coding :)