Same problem here
I've just started using DW (a newbie coming over from GoLive) and DW and CSS is giving me headaches. I've used a DW template for the site and CSS MenuWriter for the menus. Like the other user, my menus (this time horizontal) are dropping down BEHIND the background image. But not on the Mac I code on. It works fine there in Safari, Firefox, and even the Chrome Beta. But on the Windows XP machine here, they go behind the background image. I tried getting help on the DW mailing list - but the best response I got was "go take a 6-8 week course OR read a 558 page book for help". I'm hoping I can get a bit more assistance here. Thanks in advance while I go re-read this thread to see if I can apply any of it to my problem.
Oh - the site is set up for testing at: www.modbookcentral.com/.