hmmmmmmmm
so the layer does have the little lock icon on it?
if *any* of those boxes next to "lock:" is checked you will not be able to move the layer- not *just* the actual padlock icon
Also, if your "Auto Select Layer" box is checked way up top in the options bar- this sometimes happens- especially if the item you are trying to select is tiny- because it's easy to accidentally select the background- which is locked. Sorry about the runon LOL!
HTH
