I know how to fix this on an individual file basis, but it is unnecessary extra work to need to do this for every Fireworks file that I work with. I work with many previously created Fireworks files everyday and the need to do this for each one is very time consuming. Adobe: please remove this as a default for CS5! Or tell us how to fix it!
I have just updated my fireworks and have this same issue. It used to be filename_r1_c1_f1, now it's filename_r1_c1_s1. That's fine for new sites, but what do I do with the old ones that fireworks seems to want to convewrt the names?
File|HTMLsetup|Document specific you can change defaults
If you rename the added slice that is the name that is exported