My myTouch Slide wasn't mounting, so I decided to open Disk Utility. My phone shows up but when I click "Mount" it gives me this error:

Error mounting: mount exited with exit code 1: helper failed with:
mount: according to mtab, /dev/sdb1 is already mounted on /
mount failed

Here's my mtab:

/dev/sdb1 / ext4 rw,errors=remount-ro,commit=0 0 0
proc /proc proc rw,noexec,nosuid,nodev 0 0
none /sys sysfs rw,noexec,nosuid,nodev 0 0
fusectl /sys/fs/fuse/connections fusectl rw 0 0
none /sys/kernel/debug debugfs rw 0 0
none /sys/kernel/security securityfs rw 0 0
none /dev devtmpfs rw,mode=0755 0 0
none /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0
none /dev/shm tmpfs rw,nosuid,nodev 0 0
none /var/run tmpfs rw,nosuid,mode=0755 0 0
none /var/lock tmpfs rw,noexec,nosuid,nodev 0 0
binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,noexec,nosuid,nodev 0 0
gvfs-fuse-daemon /home/matthew/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=matthew 0 0
/dev/sdg1 /media/Seagate\040GoFlex ext4 rw,nosuid,nodev,uhelper=udisks 0 0

EDIT: Here's my fstab:

# /etc/fstab: static file system information.
#
# Use 'blkid -o value -s UUID' to print the universally unique identifier
# for a device; this may be used with UUID= as a more robust way to name
# devices that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
/dev/sda1       /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda5 during installation
UUID=3b0db205-2bdb-4c98-a506-6bdd3520d540 none            swap    sw              0       0