Problem with Top Menu Bar Display in Safari

Hoping you can help. I have an intermittent problem with the menu bar getting bunched up in Safari and IE. Works perfectly in FireFox. I have attached a screen shot for your review. The problem is very random. If I refresh the page several times, it will temporarily correct itself. If I clear the cache, it will temporarily correct itself. However, nearly every time I work on my site, I experience the same problem -- sometimes on my blog or post pages, sometimes on my Contact page, and now on my What We Do Page (this is a first) -- very random.

I am using:
Safari 5.0
FireFox 3.6.8
IE (testing various versions from the Develop menu in Safari)
Atahualpa 3.5.3
WP 3.0.1

I read a previous post about this issue but their solution did not work for me (checking the ATO Page/Post Style Body box -- mine is totally blank).

If you need additional information, please let me know. Thank you.