Mega Menu doesn't work properly on sublevel dropdowns. Look here: http://faststreamads.com/stage/helix/ Hover over the "Home" and then "Shortcode". Note it floats left off of the screen and cuts off the menu items. Actually a big issue considering I will have to rip out the menu and install a different mega menu if bug not fixed. In other instances it works seemly OK but then when you resize the browser it simply resorts to bleeding out to the left side of the screen again not displaying the columns. At the top level this is not an issue. Issue only occurs on the sublevels.
The "Shortcode" menu is using 6 columns 100px wide. There is ten items under the "Shortcode" menu.
I've got the same results on IE7,8,9 - Firefox 26 - Chrome - Safari
This is the most current version of Helix II Framework. I've tested a few other of your commercial templates and they all have the same issue as well.
PS: This is in Joomla 2.5 and I suspect the menu.js is probably where the issue lies. This is version 2.1.4 the most current version.