Before trying to troubleshoot scanning, please make sure you are using the latest version of the driver from the repository. If you installed the driver manually, you are on your own; there are too many library conflicts for scanning to be reliable. The repository addresses most of them, and I won't provide details here on how to reconstruct all of them manually (that information is available in various locations on this website and in the support forum).
I Can "See" a USB-connected Scanner but Scanning Software Does Not Detect It
If tools such as sane-find-scanner report scanner detection but scanimage -L, xsane, and the like do not work, ensure your scanner is connected into a main USB port, not one associated with a hub. Most often this occurs with an external USB hub, but in same cases particular ports in a desktop computer are on a hub as well, and so different ports (in particular front vs. back) may make a difference. (Note that if the USB port/hub issue is your problem, printing will usually work fine; the only issue will be scanning.)
My Printer Seems to Be Configured but I Can't Scan
There is a problem with the libpng12/libpng3 packages (v1.2.44-1 & some earlier versions); an essential link was not included. If there is not a more recent version of the package available through your distribution, install the libpng12-dev package to get the correct link. Alternatively, you can try:
to create the correct link. If none of these solutions fixes the problem (or the link already exists), post to the forum asking for help. This problem will manifest itself as being unable to print, scan, or launch the Samsung Configurator.
My USB Printer Is Inconsistent or Fails to Scan and I'm Using an Old Distribution
Occasionally and only in distributions released prior to 2008 (Debian 4.x (Etch), Ubuntu 7.10 (Feisty) and earlier), the USB support will be quirky or broken using these packages. I don't know why this is, but there isn't a good solution due to limitations in the way the Samsung drivers themselves work. Your best bet is to update your distribution.
I Installed the samsungmfp-scanner Package but I Can't Scan
Ensure that you have installed the scanner package and that you have added yourself to the "lp" group, then logged out and back in. For some Linux distributions/releases, you may also need to try the "saned" group in addition or instead of the "lp" group. Depending on the exact Samsung driver version and your system configuration, you may also need to run the scanner software as root (or sudo). You may also have better luck with a different driver package (as of September 2011, there are 3 versions available).
I Can't Scan, My Printer Is Connected by USB, and None of the Above Helped
This could be due to a several problems, which are specific to particular distributions/releases, configurations, and kernel versions. The two most common issues and possible work-arounds are given here:
In some cases, multifunction printers that print but are having trouble scanning may work if the USB 2.0 kernel module is temporarily removed:
sudo modprobe -r ehci_hcd
Scan using xsane, the Configurator, or some other program
sudo modprobe ehci_hcd
The last line restores the module so that your USB ports will work for other devices.
Current versions of the Samsung driver require legacy software support for scanners to work using the USB interface. Specifically, the kernel option CONFIG_USB_DEVICEFS must be set to "y" when the kernel is compiled. This option is not enabled in the kernel used by Ubuntu 9.10 or later, and so Samsung multifunction scanners connected by USB will not work unless supported by non-Samsung drivers. In other words, installing the scanner package could potentially take your scanner from working (via non-Samsung drivers) to non-working. Network connected scanners work regardless. If you need Samsung drivers to use your scanner, must connect by USB, and are running an a kernel without this option, you have several options (note that this list is as of early 2010; the issue seems to be less in mid-2011, even though the reason for it is not apparent to me and I have not had time to investigate):
Compile your own kernel to enable this option.
use a distribution that still enables it by default (such as Debian, as of the 2.6.32 kernel).
Try the Xerox driver solution described in post 431 of the support thread (use udevadm or udevinfo to get the relevant information).
Try the bind/mount solution described here and with more details and a script here.
Wait until Samsung releases updated drivers that fix this problem. (But the problem has existed for well over a year without a fix forthcoming.)
I Can't Scan, My Printer Is Connected Over a Network, and the Printer Is On a Different Network Segment
Network scanning requires that your computer be on the same IPv4 local area network as the printer (so that the all the "x"s in x.x.x.??? are the same for your computer and the scanner and there are not multiple routers between the two) and that your computer firewall does not block incoming UDP packets from the printer. (If you have a firewall configured to drop all incoming connections by default, you will need to make an exception for your printer's IP address/name.) There are work-arounds for the same-network issue described here and supplemented here.
I Can't Scan, My Printer Is Connected Over a Network, and None of the Above Helped
First, ensure you are using the most recent versions of repository packages. The latest packages greatly simply problems with the detection of network scanners. See this post and this one if you want an idea of what the older packages were trying to work around and solve for you, or if you really want to address the likely problem manually without updating to a more current version (the 32-bit fix is similar, but requires use of the 2.12 eglibc instead of 2.10). If you run xsane (or similar) in terminal and receive errors about GLIBC, update to the latest driver version. If you are using the latest driver, please post to the forum and indicate what version (name & version #) of the samsungmfp-network package you have installed and what the version number of the libc6 package is on your system.
If none of these solutions help, numerous other solutions have been proposed earlier in the forum support thread (in the range of posts 450-600), although most or all are focused on addressing these same issues. Also note that older Samsung-provided installers would occasionally install the 32-bit netdiscovery utility on 64-bit systems, which could also lead to failures to scan if i386 libraries are not installed (usually happens with 3.00.37 or earlier and the qt3 Configurator).