Exact same problem here....
We just heard from one customer and unfortunately have to confirm:
Submenues in Megamenues cannot be reached in IE (it works in FF, Chrome, Opera, Safari).
Test:
www.c-stab.net
-> Angebote -> Berufsgruppen -> .... try any submenu
We have confirmed the problem on IE 10 on template Resorts
We suspect this is a typical IE nuisance, but still need to solve it somehow.
By the way.... on
demo.smartaddons.com/#sj-resorts under K2 -> K2 category you can observe the problem as well ... to some extent, though it seems to be possible if you go beneath K2 category to open the submenu ... and of course this one isn't a Megamenu.