Double bump... This indeed looks like yet another bug.
I am experiencing the same issue with XC5.2.10.
Using IE's emulater, it looks fine until version IE8 and earlier where the emulator will not finish loading the page due to errors. The older the computer/smaller the screen the worse the issue.
I'm also getting the mobile view 'sort of' loading or the main template minus pretty much all styles.
In additon,
https://www.x-cart.com/extensions/addons/horizontal-flyout-categories-menu.html - does not work and is just a list of links.
Turning on Aggregate CSS files Aggregate JS files did not work for me. The whole template went crazy.
I'm currently paying xcart to look into these bugs (I had no other choice even despite they fact they are bugs!) so will add it onto my list of woes and see if I can someone to finally look at it for us.
XC5.2.10
Initmates template
Horizontal Flyout Categories