Had something similar the other day, could not receive the localiser on any receiver, it popped up on the left PFD only eight miles out - other planes reported no issues, so we had some sort of antenna issue - made the quick decision to fly a non precision instead after coordination with ATC. An invalid ident wouldn't worry me too much as long as you checked it manually, if you lose the signal or it fluctuates you might be able to continue on LOC/VNAV after a quick reset of the autoflight system - I wouldn't really do that in the last eight miles though... Iif you are visual with the runway the solution is obvious.