Hello pilots

While a lot of people are chasing to get FMS for 737, I found it very impressive to do VOR arrivals and approaches combined with ILS. But what I have noticed, that I was making them "partly blind". While established on ILS and already on a glide slope, I do not have any DME reading for it. I did it in many different airports and even started to check that ILS really does have DME. As for example Frankfurt international does have it on all runways in P3D V4.5, but my DME always shows nothing. It is operational when tuned to VOR DME, but not ILS.
Is there something I am doing wrong? Need to mention I have installed "total overhaul" from avsim library and it works fine for me, so it's hard to believe there is a mistake in that. I really hope it's just some switch that I don't know or forget to switch on...  ::)

Regards, Viktor.