Hi Skormy -- I don't have a Mac so I can't help you, but hopefully someone else chimes in. Perhaps a re-install from the original CD would make the difference, if no one has any better ideas.
I had this problem appear after I turned off a lot of the autorun and startup programs on my PC to speed up its boot time. I started IJ Network Scanner Selector EX as per verice's suggestion, and then the printer could see my PC instead of just the ...