* Claire is dead (allowing for the idea she may be "dead" in the same sense that Christian Shepard is dead). She did not die at the barracks. Hurley, Sawyer, Locke et al have been interacting with and possibly touching her (definitely touching in Sawyer's case her) since the RPG round hit her house. She suffered a blow to head in the explosion and then was very disoriented. Sawyer commented and said "she got her bell rung but she'll be fine." After that, when asked how she was feeling, she said she had a headache but was fine. Victims that have had head injuries often feel fine but then later they have brain haemorrhage and it eventually kills them. It is a symptom of severe concussions.
o Claire does die (technically) from belated brain haemorrhaging in Something Nice Back Home, but her body and soul are subsequently restored by the island similar Christian. At that point, Jacob sends Christian to escort Claire to The Temple (leaving Aaron behind in the jungle), where she later projects her image to Locke in the cabin and to Kate off of the island. This happens because the Island has decided that Claire "still has work to do" and is important to protecting the island.
* Claire's last nurturing act as a mother is to feed (nurse?) Aaron, and lie down with him for the night. She dies, is absorbed by the Island and "awakes" to find Aaron apparently missing but actually in the arms of his grandfather, Christian. Together, they find a safe place to leave Aaron where Sawyer is sure to find him and leave for their ultimate meeting with Locke at Jacob's Cabin.
* Miles' interest in Claire is based on the realization that she is about to die. He asks to carry Aaron because this is his first experience with pre-death and he does know what will happen when Claire crosses over(dies), and he doesn't want Aaron to be dropped and killed.
* Claire is dead, having died in the barracks when the mercenaries blew up her house. Why the others could see her is unknown. Perhaps it was the islands will. This explains why Miles was so interested in her. Wondering why, since she was dead, everyone (including herself) acted as if she were alive. Knowing she was dead, Christian Shepard went to her. She wanted to take Aaron with her, but he explained that she could not and convinced Claire to leave Aaron where the others could find him.
Is not dead
* Claire is not dead. The reason why Miles was acting strange was because he could sense Christian near her and wanted to carry Aaron as a precaution.
* Claire is not dead. Locke is dead and now taken over by Jacob's nemesis. Claire was forced to give up Aaron, as Jacob's enemy needs him for something. She tells Kate (through her dream), "dont you dare bring him back." This was so Aaron can be protected off-island from Jacob's nemesis.
* Claire is not dead. Jacob's nemesis posed as Christian to draw her into the cabin. As Jacob was located at the base of the statue, the cabin is most likely not Jacob's cabin at all, but rather the "prison" for Jacob's nemesis. Jacob's nemesis has her leave Aaron by the base of the tree knowing that whoever escapes the island (the Oceanic Six) would assume responsibility for Aaron and take him off the island. Jacob's nemesis appears as Claire off-island in a visit to Kate and urges her to keep Aaron away from the island simply because, as the show has repeatedly made clear, Aaron is special - Aaron alone has the power to bring upon the downfall of Jacob's nemesis, hence the complex chain of events coordinated by Jacob's nemesis to lead him off-island. Contrary to the theory above, this isn't about protecting Aaron from Jacob's nemesis, it's the opposite - this is about Jacob's nemesis protecting himself from Aaron. This might be incorrect, but the only times that "bodies" have appeared off-island (Christian visiting Michael on the freighter right before it explodes, Christian's visit to Jack after the smoke alarm goes off in the hospital, Ana Lucia pulling Hurley over, etc.) occur AFTER Claire is led to the cabin and breaks the circle of ash, thus freeing Jacob's nemesis to travel off the island in the form of visions/apparitions. The show will boil down to a conflict between Jacob and his nemesis, and since Aaron was to be raised by Claire because she is "good", Aaron will be the most important player on Jacob's "good" side.