I have a Brother MFC-7420, which also works as a scanner. I have attached this machine to a computer running Ubuntu 12.04 LTS 64bit via USB.
I installed the following package:
brscan2-0.2.4-0.i386.deb
Now when I start xsane, the device is detected. However, when I try to scan or run a preview scan, I get the message Could not start scanner: Invalid Argument. The same problem exists if I run xsane as root, so I don't think it's a privilege problem.
There's no output on the console while running xsane (see screenshot below). The dialog box showing the error appeared just after pressing the "scan" button in xsane.

What can I do to get this scanner running?
xsaneappears to be invokingsanewith bad syntax. To be sure, can you post a screenshot showing the error? If that is what's happening, it should be reported as a bug, probably inxsane. (This question also has some good information about bug reporting.) In addition to a screenshot, please runxsanein a Terminal window (Ctrl+Alt+T) and give all the text in the Terminal; please also specify what messages appeared when. Please edit your question to provide all this info. – Eliah Kagan Jan 14 '13 at 20:43