My site, built on wordpress, is coded XHTML 1.0 strict and CSS3. It validates except for script tags not CDATA enclosed, and unclosed < br > tags, and those found in jquery-ui.css

The site is live on a domain www.example.com while the development site is live on www-dev.exampledev.net Both installs have the same code. 

On IE8 on Win7 both sites render the same for both www and www-dev sites..

While IE8 on Vista the www-dev site renders correctly, but the www site has a problem with the placement of the major page navigation - there's a gap that shouldn't exist. 

I don't have access to an IE8 Vista box, so I can't easily look at the code using the IE equivalent of FF's webmaster tools

Any suggestions on how to deal with it? I'm wondering if it's not the same issue as this one: 

[Strange rendering issue occurring in IE8 only](https://stackoverflow.com/questions/5651429/strange-rendering-issue-occurring-in-ie8-only)