I have the same problem.

Hello there,
When in doubt..... ALWAYS read the instructions

Well the user guide for this machine (which you should already have) talks all about 'unable to init xx' on pages 139 and 140.
Have you trd following the instructions exactly ?
Download here http://download.brother.com/welcome/doc002373/mfc490w_usaeng_usr_b.pdf

If it still has a problen get in touch with Brother support.
http://www.brother-usa.com/support/default.aspx

Hi,Check to see in the connectioncables are all plugged in correctly.Open the printer and see if drumunit and toner cartridges are installed correctly. Sometimes not well installedconsumables are the cause of that particular problem.See if the print driver on yourcomputer is correctly installed. Try and reinstall the driver.Check if your printer is working in onlinemode. Sometimes printer changes online to offline method. If printer is atoffline mode click Start button on your computer, enter Control Panel. Click onHardware and Sound and choose Printers. Right click on Brother MFC-9840CWD andmake sure that the Use Printer offline is not checked.Hope this helps.

I had the same problem, and couldn't find a solution anywhere. My laptop said the wifi Brother MFC-255CW printer was offline, when the printer was definitely online and connected.
In the end I simply went into Control Panel / Printers, selected the Brother printer, and deleted it off the network. Then I chose "Add a Printer" from the network, and reselected the only printer on my home network - which was the Brother MFC-255CW that I had just deleted. The computer reinstalled the driver, and everything was fine again - haven't had a problem since.

check your cartridges

If you want to make it online, than make sure it is on and connected to your computer, Once you are sure about this than

Go to control panel than Printers and Faxes

There You need to right click on printer and than Use printer online

IT will Put you printer back online.

Try and shut down the printer and turning it back on. Hold down the power key for 5 seconds or so. Then turn it back on to see if you have your connection showing on your task bar on the bottom of the screen. there should be a green halo around the printer. You may need to reboot your router too.

If you are running Vista and SNMP is turned off
1. Check to see if SNMP is turned off this is a component of Vista
a- Control Panel
b- Program and Features
c- Left side of screen you should see turn windows features on or off
d- Click on this a window box should open scroll down and see if SNMP feature is checked if it is then turn it off (unchecked) follow these steps
e- Under printers select Brother MFC-940CW printer right click
f- Select run as administrator
g- Select properties
h- Select ports
i- Select button configure ports
j- Under port settings uncheck enable SNMP
k- Click ok printer should be on line
l- To find MAC address for MAC filtering on router
m- Run the brother remote setup program and note the IP address
n- Run the command prompt as an administrator at the prompt type the following “apr –a” without the quotes and then hit return and note the physical address (MAC) for the above IP address you noted. Log on to your router and enter the MAC address from the step above and save.
o- Run the brother remote setup program again and change TCP/IP from “auto to static” please note you must have box checked at the top of the window edit network settings.
p- Restart the computer

For my MFC, my PC says its ready and working properly. It really only works when I'm not connected to my cable modem. All PCs use it then. It's offline otherwise.

Hi,

I had the same problem with a Brother MFC-6490CW AIO printer. Here is how I resolved it:

Open the printers folder.
Right-click on the Brother printer and display the Properties page
Select the Ports tab.

In my system (Vista Premium), the selected port was a WSD port (whatever that means). Further down the list, there was a TCP/IP port that was obviously created by the Brother installation software. I selected the Brother-created TCP/IP port (which deselected the WSD port), applied the changes, and suddenly my printer was online. No idea what the difference between these two ports is, but I'll stick with the TCP/IP port until further notice.