First off have you tryed saving file as Index.html
found that link on interent for you i Export using Html function not Css sorry if nothing was a help ?
also have you tryed looking in adobe Tv section the videos in Fireworks bit at all ?
I too am having exactly the same problem. 3 days watching and working through copiuos online videos and in deparation today downloaded from Adobe, css_templates_fwcs4 which comprises of 5 templates for standard and enahnced css export complete with slicing already in place. Thinks!!! if I load this, do NOTHING to it and export and it works then clearly there is something wrong with the 30 attempts I have made this week!
As you can see from the screen capture above, EVEN the files from Adobe didnt work!!
Can anybody please advise what I should try next?