I wish I had an easy solution for you but I don't, IE 6 is a pain in the arse. All I can tell you is a strategy. You can override IE 6 styles in IESpecific.css, but its a trial and error process to find a fix. You just have to try things based on what it looks like in IE 6, make small changes and refresh. Most likely you will need to override style coming from stylemenu.css so you may want to copy parts from that and past into IESpecific.css and modify to try and fix the problems.
Hope it helps,