Idaho...
Im guessing it has something to do with how civilian and military airport VOR/DME and TACANs are done in FSX? Maybe some difference in TACAN vs. VOR/DME systems and how they are done within the simulator? I have the same problem, when I fly from Nellis to Miramar, I can never get the TACAN needle or range info on the HUD. I can switch DME modes and get TACAN range on the Baron Radio Stack that I have configured on my Hornet as a pull up screen, but no needle or info on the HUD at all. However, when flying from MCAS Miramar to Williams Gateway (icao KIWA, used to be military but long since civilian airfield), I just dial in IWA TACAN for NAV2, dial in the correct ILS on NAV1 for Rwy 30C and I get all the info. for ILS and TACAN on the HUD. Just fly from KIWA, load up the TACAN on your NAV1, change your NAV2 to that freq., then input the correct ILS on NAV1 and do some touch-n-go's. Should get all the proper info for ILS and TACAN with the NEW HUD.
Can send a screen shot if you need, but I think the simple answer is VOR/DME is done differently than military TACAN in FSX. There are probly far better explanations from some of the members of this forum.
Later
Sludge