Time machine back up problem

Well, it's definitely not encrypted now. With local USB drives you are supposed to be able to encrypt them without erasing them (which you can't do with network mounted drives), according to what I've read. Can you click on the open System Preferences Time Machine pane and then click the "Select Disk" button and is the "Encrypt backups" option grayed out if the Elements volume is selected or is it black and can be enabled (don't actually do it yet)? Notice that there will be two Elements items in the list of backup disks - one has the TM icon and one has the USB icon -- on my system when the TM icon volume is selected the "Encrypt backups" is grayed out and when the USB icon selected it's not grayed out.

I am gonna setup a test case for doing this and see what happens before I tell you to do it on your system to avoid anything tragic happening. But that will take a while to do, maybe a couple of days or so -- if you want to do a little more research of your own or if anyone else here can vouch for that being OK to do now, that's probably worth waiting to find out before doing something that trashes your backups.

Good luck...

What does the following Terminal command return (Terminal.app is located in the /Applications/Utilities folder) -- the TM disk should be mounted before doing this command:

diskutil list

You might want to change/hide any personal info (like the UUID number and whatever else you wish) before posting the results. You just do a select of the command and the results and do a Command+C and then post that back and then edit to remove stuff. The UUID is the 32-byte hex number that might appear.

Good luck...

OK, now open up Disk Utility and then select the Elements volume (don't select the drive but the volume -- ask if you don't understand the difference) and do a "Get Info" (right-click or control-click to get a menu and select "Get Info" or a Command+i should also work) -- what does it show for "File System" parameters (think it's the eighth item from the top) -- in fact just do a screenshot of that get info window (you might want to blot out the UUID values or at least most of them as they aren't needed yet).

This will tell us for sure what format the volume is as well if it is encrypted.

Good luck...

OK, now open up Disk Utility and then select the Elements volume (don't select the drive but the volume -- ask if you don't understand the difference) and do a "Get Info" (right-click or control-click to get a menu and select "Get Info" or a Command+i should also work) -- what does it show for "File System" parameters (think it's the eighth item from the top) -- in fact just do a screenshot of that get info window (you might want to blot out the UUID values or at least most of them as they aren't needed yet).

This will tell us for sure what format the volume is as well if it is encrypted.

Good luck...

In Sys Prefs>Spotlight, have you tried removing the Backup Disk, then adding it again?

Was it encrypted once? Did you un-encrypt it?