Thanks for the advice Steve. I have looked but cannot see how to reset the preferences. I am using an iMac. Can you advise how to reset the preferences. I just checked InDesign on my Del laptop which is the 2014 version and the smart guides work fine, just cannot see why they do not work in one direction only in 2015
Follow the direction in the link Steve provided....
Make sure the application icon is visible or in the dock.
With your left hand, hold the Command, Option, Control, and Shift keys on the left side of the key. That's four keys. You'll have to work a little hard to do it.
Don't let go of these keys.
Move your mouse over the Application icon in the dock or in a folder.
Press. A menu will appear with the word Options at the top.
Choose that and then choose Open.
Release the mouse and the keys you were pressing with your left hand. (Shake your hand out if it has gotten cramped.)
The InDesign launch screen will appear and then a dialog box asking if you truly want to delete the preferences.
InDesign will launch with its preferences all spanking new.
Just to let you know, adobe have agreed it is a bug, the smart guides do not work properly in 2015 using OS X