I suspect the problem is not SP2, but more likely that the driver for your scanner is not supported/recognised by the upgrade, try looking on the manufactures website for a new driver.
Is it a USB scanner? Have you tried any other USB devices? It's common for there to be USB problems after installing SP2. As it is still XP, I wouldn't have thought that it was a driver problem but, as Memesis9 says, it is worth checking the web site. If it is a USB problem, I would suggest going into your System Properties/Hardware and then uninstalling/deleting all the USB devices then restart and let Windows find them again - it worked for me.