What have i ticked

[baz]

hi
i've had this problem before but just unchecked a box or button
but cant find it now.
what normally happens is when i want to duplicate something
i normally left mouse button select drag then right mouse and release
this normally creates one copy
problem now is left button select and when i drag its multi-duplicating as i drag
what have i selected
thanks
baz

forgot to say its corel X3