Find the ASPmenu control that is the topnavbar in your masterpage. One
of the attributes in the html markup refrences a SiteMapDataSource
control. Find that control on the page, it should be just below the
aspmenu.

You need to add an attribute called ShowStartingNode="False" to the
SiteMapDataSource. That will filter out the home  page node from the
data used to build  the top  navbar.

I checked this and the attribute is already there. Here is my code
just in case I'm looking at the wrong section.

<SharePoint:DelegateControl runat="server"
ControlId="TopNavigationDataSource">
<Template_Controls>
<asp:SiteMapDataSource
ShowStartingNode="False"
SiteMapProvider="SPNavigationProvider"
id="topSiteMap"
runat="server"
StartingNodeUrl="sid:1002"/>
</Template_Controls>
</SharePoint:DelegateControl>

I'm not  sure what might be going on. Check your top  nav ASPMENU control
to make sure it is still using the topSiteMap as its datasourceID.
Also, since the datasource is in a delegate control do you have a
feature that might be adding a different sitemapdatasource that is
configured differently.

I checked and it is still using the topSiteMap as its datasourceID.
I don't really have any custom web parts that would affect this. This
top bar will be used across many site collections; would it be better
for me to create a custom top  bar? If so, do you know of any
documentation on how to do this? Thanks.

Here is my code:

<SharePoint:AspMenu
ID="TopNavigationMenu"
Runat="server"
DataSourceID="topSiteMap"
EnableViewState="false"
AccessKey="<%$Resources:wss,navigation_accesskey%>"
Orientation="Horizontal"
StaticDisplayLevels="2"
MaximumDynamicDisplayLevels="1"
DynamicHorizontalOffset="0"
StaticPopoutImageUrl="/_layouts/images/menudark.gif"
StaticPopoutImageTextFormatString=""
DynamicHoverStyle-BackColor="#00467f"
SkipLinkText=""
StaticSubMenuIndent="0"
CssClass="ms-topNavContainer" Width="16px">
<StaticMenuItemStyle CssClass="topNavItem"
ItemSpacing="0px"/>

<StaticSelectedStyle CssClass="topNavSelected"
ItemSpacing="0px"/>

<StaticHoverStyle CssClass="topNavHover"/>

<DynamicMenuStyle CssClass="topNavFlyOuts" />

<DynamicMenuItemStyle CssClass="topNavFlyOutsItem" />

<DynamicHoverStyle BackColor="#FFFFFF"
CssClass="topNavFlyOutsHover" />
</SharePoint:AspMenu>

Has anyone had problems with using the ShowStartingNode attribute and
it now working correctly?

That should be 'not' working correctly instead of now.