In a library each "piece" (ie the picker, the drives and the slots) will have a unique element address. When a backup job begins cmd are sent to the library. First cmds will be move cmds to get the media from the slot to the drive, this cmd will have a source element (where the tape is) and a destination element (where you want it moved to). When you have an invalid element address that means one of the address's is invalid (easy enough). As part of keeping the software in check with the hardware there is a READ ELEMENT STATUS cmd that is performed, this command will "update" the software as to what elements are valid. Most often the error you are seeing is due to the fact that someone manually removed or moved media from the library or within the library and didn't sync the software up. Easiest way to fix this in BE is to initialize the library (right click on the device within BE and select initialize). If this does turn out to be your issue easiest way to prevent it is to let the software mange all media movement.

Hope some of this helps

Bob

didn't help but I'm gogin to install R3 soon, I'll see if this has any affect

thx