Nav links not working in Firefox, using WP MU

We’re having a problem in Firefox only. Nav links are not working in Firefox (v3.x, PC), but are fine in IE and also appear to be ok in Firefox Mac also v3.x. Other internal links (downloaded docs etc) and links to outside pages are fine, only the nav is not working.

Unfortunately this blog is not live until at least tomorrow (Wed 7/23) for you to see (https://itsnotover.phrblog.org), but if anyone has any general suggestions I would very much appreciate them. btw, we’ve tried disabling plugins (cforms II and Downloads) as well as turning off Maintenance Mode temporarily. Nothing made any difference. Any other troubleshooting suggestions would be welcome!

Thanks!