I'm with you brother, I have a Brother MFC-640CW too. I'm using the Debian software for my OS. I'm a newbie and I have no clue on how to get this printer to work.
I can connect to it (wirelessly) by typeing
ftp://[my IP address] but I can't print to it.
Let me know if you find something. I will keep looking and post here when I find it.
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Okay, I found it at ...
http://solutions.brother.com/linux/s...ers.html#model
For the 640CW, use the bscan2 stuff