SharePoint 2007 CSS/Master page menutoolbar class disappears??

Hello,

Not sure if this is 100% the right place for this, but my team created a custom master page for our 2007 environment & on the menu tool bar (new, upload, actions) default webpart, when rolling over one of them, it makes the others disappear for some reason. I've added a screenshot below so you can see what I'm talking about, but remember, it usually happens when you rollover one of the links.

I can't for the life of me figure out what is causing this issue. I have no code in the css using .ms-menutoolbar or anything like that. Most users are still using IE8, with a few IT folks on IE9.

Anyone have any idea on what could cause this issue, or if there is any code I can add to the CSS to make sure it's always visible?

Thanks in advance.