Is the vfat module loaded? You might want to check the filesystem type with "file -s /dev/sdb1". Also are you able to access the files on any other system? If the data on the usb drive is not important, then try formatting it. "mkdosfs /dev/sdb1" will create a fat16 filesystem while mke2fs will create an ext2 partition.
Thanks a lot! I learned quite a lot this weekend, :-). Summary of mistakes: (1) I wanted to mount a wrong device (sda1 instead of sdb1). (2) Did not have the vfat module and the usb_storage module loaded. Cheers Sam