Follow the steps outlined in the common installation issues to get to the configuration directory:
common_installation_issues.pdf
After that, go to the \Configuration\Commands\ directory and open the WA Universal Email.js file. Go to line 2765, which should look like this:
document.Body.document.prevtab2.style="border-top-width:2; border-left-width:2; border-right-width:2; vertical-align:top; border-top:solid; border-top-color:#D8CDAC; border-left:solid; border-left-color:#D8CDAC; border-right:solid; border-right-color:#D8CDAC; padding-left:3; padding-right:3; padding-top:3; padding-bottom:3;";
Add a line right before it that looks like this:
if(document.Body.document.prevtab2)