What version of menu writer are you using? This is most likely a z-index issue, but I thought it was corrected in the most recent version of menu writer.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.