Hi,
Please check several things:
1. Whether the menu renders fine when you put it into a blank page;
2. Whether your page is in standard compliant mode. If it is not, try to switch the page into standard compliant mode and see if that resolves the issue. If you are not sure, see here for more information on how to switch page into standard compliant mode:
http://doc.essentialobjects.com/library/1/menu/menu_perf_tips.aspx3. Whether it works fine when you remove your external CSS style files;
Those tests will not immediately solve the problem for you, but should provide additional information as to what may cause the problem. In any case, if you can create a test page that duplicates the problem, we will be very able to run and debug the page here and tell you exactly what caused the problem and how to fix/workaround it.
Thanks!