Validator Callout Extender behind other items

I'm trying to use the validation callout extender on my page but it appears behind other layers on the page.  I've read the posts and tried editing the css, but it doesn't seem to help.  The base css sheet has no other z-index properties set explicitly.  I even tried putting it on the td tag.  I have the following in the referenced style sheet:

.valCallout

That didn't work, so I tried this in a style reference on the page and placed it in it's own div tag id around the validator and then on the parent td-no change :

 #

BTW - tried IE8, IE7, FF all the same.  I'd appreciate any ideas.