In order to get dynamic drop down menus in MOSS 2007, I modified the
master page's AspMenu section to the following:

<SharePoint:AspMenu
ID="TopNavigationMenu"
[snip]
StaticDisplayLevels="2"
MaximumDynamicDisplayLevels="4"
[snip]
</SharePoint:AspMenu>

It's been working for quite some time. However, I just came across a
problem and I'm wondering if anyone knows what to do about it.

On my top-level page, I put an announcements web part. However, as
soon as I actually add an announcement to the announcement list, the
dynamic menus no longer work on the home page (but do work from
subsequent pages where there is no announcement webpart.)

I've tried moving the web part around to no effect. I've tried
deleting the announcement text, to no effect. I've tried deleting the
announcement itself, and the dynamic menus work again.

Any help is appreciated.