Thanks, I'll try to reproduce that on our end.
One other thing you can do is to temporarily detach the page from the template and then apply the Add To Cart button and then attach the page to the template again. You can do this by:
1) Opening up the page in an external text editor and copying the line of code that looks similar to this to another text file:
<!-- InstanceBegin template="/Templates/Main.dwt.php" codeOutsideHTMLIsLocked="false" -->
It should be right after the open <html> tag.
2) Delete the code from your page, save and close the document.
3) Open the page in Dreamweaver and add the Add to Cart button.
4) Save the page and close it in Dreamweaver.
5) Open the page in an external text editor and then copy the code back in to the same location.