Vertical lines in tabbed menu ( only in Windows7 IE8 x64 )

I’ve just changed the design of my entire site, and while on the development server, I hadn’t noticed any problems, but now that the site is live, there are some lines that show up in the menu when viewed on Windows 7 IE8 x64. 32 bit doesn’t show the lines, and all other browsers don’t show the lines. The lines seem to go away when I hover over a tab, or scroll down the page and come back. Also, the lines aren’t consistent. Sometimes there are 4, sometimes 5, etc. I tried turning off javascript, and that didn’t make a difference.

Site is, and a picture of the lines is attached to this post.

Any ideas?

I’ve been working on this all day, and figured out that any time the page content is longer than the browser window, it is causing this display issue. It still only happens on Windows 7 IE8 64 bit. It also only happens on the production server. If I test from localhost, no problem.

I’ve ripped out all extra code, and put all the CSS in the head. That would be here:

The menu does need to be positioned absolute, and inside the width-limiter class. If I remove the width limiter, the lines go away, but that’s not really an option. This is so strange, because it seems like basic CSS.

Any help or clues would be appreciated.

Ended up applying a negative margin to some of the divs, and that cleared things up. Seems like a bit of a hack, but it’s IE, so I guess anything goes.