I have the most basic page I can create and the problem still exists
here is a screenshot of my issue

the gray box on the right is a regular div with a zindex of 999
I actually tried to wrap the EOsplitter into a div with a zindex of 1
my problem is that the gray div can not be accessed, so if I had controls like a textbox or something I cant access them.  You'll see from my screenshot that I tried highlighting the text in the gray div, but the EO splitter content gets selected instead.
The content of the gray div shows behind the EO splitter panel.  I would actually like to have the gray div lay on top of the EO splitter and hide what is behind it, which is normal practice. 
here is the markup
<div style="float:right; padding:20px; border:solid 1px black; z-index:999; background:#eaeaea;">
            this content is not accessible.
            <br />
            controls here are not accessible
            <br />
            the splitter actually gets the cursor
            <br />
            z-index has no impact
        </div>
        <div style="z-index:1;">
        <eo:Splitter runat="server"  Height="500px" Width="1000"  id="Splitter1"  BorderStyle="Solid" DividerSize="7" BorderWidth="0px" BorderColor="#dadada" DividerImage="00080411" ControlSkinID="None" style="z-index:1" >
                <eo:SplitterPane id="SplitterPane1"  Width="445" runat="server">
                    lots of content goes here lots of content goes here lots of content goes here lots of content goes here lots of content goes here lots of content goes here
                    </eo:SplitterPane>
                <eo:SplitterPane id="SplitterPane2"  Width="445" runat="server">
                    lots of content goes here lots of content goes here lots of content goes here lots of content goes here lots of content goes here lots of content goes here
                    </eo:SplitterPane>
            </eo:Splitter>