I have the same issue and here is What I did and it works great for me.
Include the Crystal Reports Viewer in the DIV tag as follows.
There is a problem with the style of Crystal Reports Viewer control and here is a simple way to fix it instead of applying the style on the control itself which doesn't work anyway. Simply enclose it with
tag which acutally works.
<div style="position:relative; z-index:-1">
<cr:crystalreportviewer id="crv3GTTools" runat="server" autodatabind="true" displaygrouptree="False" toolbarstyle-width="1024px" xmlns:cr="#unknown" />