hi claire,
instead of the separator (which is sometimes responsible for breaking a site in ie7) you can use the following alternative.Joomla 1.5
1. Login into your Administrator
2. Go to Menus > Main Menu > New
3. Choose "External Link" as your Menu item
4. In the link field, insert
javascript:void(0)
5. Fill in your other details and save.
you can also try the "alias" menu type, it is useful for example to use for a parent item to point directly to the first submenu item.
kat