I'm using thunar 1.0.2 on Archlinux.
I have an usb storage that has LABEL entry on fstab.Everything works well on nautilus and mounting from command line.
But this is what I get on thunar: 
"Mount Failed: You don't have the right permissions to mount the volume..."

This is the entry on fstab;
LABEL=Ext3 /media/usbdisk   ext3    users,noatime,noexec,noauto 0 0

I've tried changing a lot of mount options,even when the "defaults" options, but nothing change.I have tried the direct UUID instead of LABEL but I get the same result.
It works only putting /dev/sdX instead of LABEL.

Give a look here:
http://ubuntuforums.org/showthread.php?t=899287&page=2