J.D.
I have never personally experienced this, but I have a friend whose brother often got nosebleeds during the night. His ped said that it probably resulted from a combination of dry air, allergies and wood floors in his bedroom. My friend says it was wierd, but anytime they would go out of town to somewhere more humid and stay in hotels (which are mostly carpeted) he would not have any nosebleeds until they were home a few days. Not sure if any of this helps or not, but thought I could share and maybe ease your concerns a bit. I probably should mention that they lived in southern NM where it is VERY dry-so I don't know if the two are even comparable, but you never know.
BTW-my friends brother is over 30 now and hasn't had a nosebleed since he was about 12.