Thanks Michel,
The downgrade caused significant other problems, however, I was able to successfully restore from a former backup. I re-linked the IR Linc and then restored the PLM. It now appears to be functioning again, although the links on the IR Link to the ISY are not correctly appearing (although it is now functioning).
I placed the IR Linc in setup, re-stored it IR code in the IR Linc, then in the ISY GUI, selected "Add IR link button" and immediately selected finish. After a reboot, this then seemed to restore the link ( although it does not display the controller or responder detail).
Again, it appears to be working again now so I will leave it alone .....you guys may have some issues though with the .15 correctly reflecting IR link details and operation.
Thanks again for the support,
Pete