I have a Brother 3100C and it hasn't printed in ages under os x. I was looking over the quick set-up installation instructions the other day and got an idea. Note...I haven't tried this yet, I will when I have time.
In the install instructions, it makes a BIG deal about not having the printer plugged in or connected to the Mac when installing the drivers.
The idea is to start from square one, trashing all the drivers and re-installing while the printer is OFF. After restart (if one is required with os x), then connect the printer and then plug it in.
If this applies to your situation and ends up working, let me know.