I use Firefox 10.0.2, but I don't think the version matters. In my bookmarks, right at the top, is a folder I have named AAAA Start. Inside are all the links I want to open when I first start up.

One click on the bookmark tab and everything opens as dropdown menus. Second click on "Open all in Tabs" and it is job done. My six favourites are waiting for a click. Whichever one is at the top of the list gets opened. I have it set for eMails, but I could just as well have it set for X Marks.

Regards

Chas