yeah they show up now (attachments were pending admin approval).
the only thing i can think of is that when fireworks resizes it it uses the pixel grid to fit it to so when it's sized back up again there are some rounding-up (or rounding-down) errors. could i have a play with your file? if so can you email it to me at gekkoweb[at]gmail[dot]com
i would suggest learning illustrator - it shouldn't take too long to make the transition (i've made it myself recently) and getting the basic techniques down to make something like the ninja shouldn't be too difficult. I've been using fireworks since the first version but have got a lot more into illustrator recently (though i'm hardly what you could call an illustrator myself ) and i can see what all the fuss about using ill vs fireworks is about, though i've seen some equally amazing things done in fireworks.
the other thing i would suggest is when you need to size up, do so first in a multiple of 200% or preferably 400% then size to the exact size tyou need (or use illustrator to do resizng, bit of a faff i know