Hi,
V5
If I want to copy something in a horizontal direction, I select the item, go transform copy, click on the item, hold shift down and hit tab, letting go of the keys now, and proceed to place copies, BUT after the first placement of the copy, its all over the place, so repeat shift tab for every copy thereafter until copies done.
once should be enough .thats what tab is for, it decrees dirwection IS FIXED.
After placing your first copy, you can click the UseLastDirection command line option (or type s ENTER) to re-use the direction constraint on all subsequent copies.