Menu automatically goes into expanded format despite overriding CSS to go horizontal

Hello there!

I’m not sure if it’s due to my lack of skill in this arena or something else entirely, but I have been facing this issue with the menu on my site’s homepage. It automatically expands despite its CSS denoting that it should be horizontal. I’ve looked into the HTML and the CSS and all I can pinpoint it to is the way that the column is programmed on the site.
The strange thing is that I have nearly mimicked any adjustments from its sister site to reflect the way that the menu was before. I had that temporarily fixed, But then I made one adjustment and now I can’t get it back despite the homepage’s HTML being almost identical to its sister’s. I have been trying to figure out for weeks how to get the menu to remain in the horizontal position, but nothing I do seems to work. I’ve tried creating a new menu, scrapping the old one, importing the sister site’s menu configurations (both settings and styles), clearing the cache (about 500x), trying on different browsers (I work mainly on Opera), and have disabled and reenabled every plugin on the site. I have tried adjusting the CSS to the column, but nothing I try seems to take. Nothing.
I cannot go to a previous backup because of the 20+ pages of content created since the menu issue and the person who made it took their Pro UABB tools with them, which is what originally was used to construct the homepage menu. Oddly enough, though, the sister site has NEVER gone into expanded mode. It has always remained horizontal.
I even took a look at the HTML and CSS to see what might be messing with it, and so far all I have is that there’s some old CSS buried somewhere on the site that I cannot easily find. It’s due to a particular column’s styling that’s overriding any other modifications I put on the homepage menu and taking every last ounce of patience I have. I’m not sure what else to do aside from just destroy the homepage and start fresh.
The other odd thing is that from time to time it will appear to fix itself only to revert back tot eh expanded menu at a later point.