Random spastic disappearing text/link

[dryadsong]

Hi there. I have a question that I have looked up, and although I get a lot of hits for what is called a 'peekaboo bug', it doesn't entirely describe what's going on in a couple of my pages.
It seems to be different for different people, too.

The problem is always in IE. My menu is in the top right corner of my pages, and in the pages with phpBB and Coppermine, the top part of the menu disappears. If you hover over the links, they reappear, but when you move the mouse, they disappear again. The size of the affected area is different on different people's IE, and oddly, coppermine has only been affected at my work's computer.

If anyone can duplicate the problem and tell me that I'm an idiot because I forgot a slash or something, I'll be thoroughly indebted.

The two pages that are affected are:

http://dryadsong.com/forum/index.php

and

http://dryadsong.com/gallery/index.php

To prove that it's just those pages, here's it working properly:

http://dryadsong.com/music/

[dryadsong]

okay...update here...

I changed the css for the containing block:


.mainmenu {
line-height: 130%;
hasLayout:true;
zoom:1;
}


this was based on some tips I found online.
since 'zoom' isn't actually "good" code...and really, I've never heard of it before...I'd like to know what the implications are. Have I broken my code for non IE-6 browsers? If anyone wants to teach my about this particular snippet or point me in the right direction to learn about it, it would be very helpful.

[_Aerospace_Eng_]

Its basically involking hasLayout. position:relative; should do the same thing as
hasLayout:true;
zoom:1;