But the drive ISN'T usbfs, it's whatever file system your drive was formatted with.
That could be one problem.
You can also force mounting by logging in as root and trying
mount -t vfat /dev/sda1 /mnt/sda1
or
mount -t vfat /dev/uda1 /mnt/sda1
(to phraitz: that's a side effect of switching from the dev file system to udev, a new feature of the 2.6 Linux kernels)
the vfat option assumes your Maxtor drive was formatted as FAT or FAT32 in Windows. If it was formatted as NTFS you'll need to use Captive-NTFS or reformat the drive, because Linux has serious issues.

I notice that your modified fstab has /dev/sda1 mnt/sda1 auto rw,user,exec,sync
there should be a / before mnt -> /dev/sda1 /mnt/sda1

There's a program in the Utilities menu (second set of menus, just to be irritating) called USBview. Does that have any device that looks like your Maxtor hard disk? It should have Maxtor somewhere in the listing of a plugged in device. If not, your drive isn't being detected correctly after boot.