This is a very trivial problem I am facing but still eating my brain.
Sometimes, mind you only sometimes, when I take my mouse over the child sub-menus, the parent sub-menu is getting hidden and the child sub-menus are literally hanging in the air. I am not sure why this is happening but it looks weird when you see sub-menu just there on the page with no parent linkage.
Could you post your menu data file coding, if you can't post it on the web? We have to see what's in the file, the best thing if possible would be to make a test page for us to see what's up. There's no way from just your desciption we would have any idea what the problem is.