My printer keeps going into offline mode since I installed Leopard

If you haven't done so already, you could try deleting the Brother printer from the Printer list, and then performing a Reset Printing System. To do this, move your mouse into the empty Printer list, hold down the Control key and then click your mouse. The Reset printing system window will appear, which you can click to perform this task.

Once this is done, close the 'Print & Fax' section and restart your Mac. Once it is powered on again, try adding your printer again and see if you can print without it going offline.

I too have a Brother HL-1440, and my problem is rather sporadic. It will print fine for a day or so, and then I'm alerted that the printer is "offline" (which it's not). Sometimes just powering the printer off and then back on will cause the print job to complete. Other times, I have to reboot before it will print. I have already deleted the printer, and reset the printing system a couple times now, and that doesn't resolve the issue (for good). I'm also having other issues with Leopard losing track of other USB devices (e.g., UPS battery backup system, USB SoundSticks), so I'm presuming that Leopard is only half-baked at this point. Big disappointment after how rock-solid Tiger was. BTW, I didn't "upgrade" to Leopard. I finally retired my 6+ year-old PowerMac and bought a new iMac which already had Leopard on it. Hopefully the next update to Leopard resolves some of these little annoying problems. These are the kinds of problems I'm used to on Windows machines, not on my Mac.

I'm having the same basic problem with a Brother MFC-6800. It may or not see the printer when a print job starts - even though it's turned on. Sometimes pause and restarting the printer will do it. Other times turning the printer off an on again will do it. Some combination of these will always do the trick.

I can print on job and then send a 2nd job to the printer right after the first job has finished and it'll claim that the printer is now off-line.

The printer is attached to the Mac Pro vis the printer's USB interface.
My wife's Windows machine is also attached to the printer via it's parallel interface. When she tries to print after I have printed a job and has completed, the Windows machine reports a failure in the print job.

I'll hold my nose, but I can say that when it was 2 Windows machines attached one via USB and one via parallel this never happened. We could "take turns" printing with no hang-ups. The problem on my wife's machine only appeared after I moved the USB printer connection from my old windows machine to the Mac Pro.

I have basically switched almost all my work to Macs and this is the only real issue that has appeared.
From the symptoms it would appear that Leopard is leaving/putting the printer into some state that confuse both itself on the USB interface and the Windows machine on the parallel interface.
Also the MFC-6800's scanner has issues with Leopard. It always reports that it cannot communicate with the scanner - whether this is a Leopard or Brother problem is unclear.
I have no experience as I'm a recent convert- and overall extremely happy with the move - to Mac's and my machine came with Leopard.

I get the same thing with Leopard and the HP Laserjet 1300. It keeps going offline.

You know what, when I was using Microsoft Windows, the final straw for me was the printer keeping going offline all the time. I said to myself, I can't afford this, particularly when it happened one day where I had a one hour deadline for finish some urgent documents, and I had to re-start the Windows computer every 10 minutes to get the printer working.

Now, whatdayaknow, it's the same with Mac Leopard --- although, a plus point is that it only takes a minute or so to reboot the Mac, rather than 10 minutes for Windows. Sore comfort.