File Sharing with old/new macbooks

ok, im a long time viewer of this board, and now i'm finally posting:

new aluminum macbook (wireless)
old black macbook (wireless)
mac mini (ethernet)
linksys wireless G router

i'm trying to share files between these 3 computers. The only way i figured out how to was through the File sharing option.

the mac mini can connect to both macbooks with no problem
the old black macbook can connect to the mac mini and the aluminum macbook with no problem
BUT the new aluminum macbook can only connect to the mac mini and NOT the old black macbook

when i try to connecting typing the afp://xxx.xxx.xxx.xxx, i get this pop up "error code -36"
the old black macbook does appear under the SHARED devices, but i get a connection failed after a while.
i checked the settings in preferences for file sharing and all 3 computers have the same settings.

any help would be greatly appreciated!!!

connect the new macbook by ethernet and see if they'll all be able to see each other at that point. if not, then there's obviously a settings issue. if it fixes the problem, then there's an issue with the airport card.