To answer the question about what blasphemy against the Holy Spirit is, I turned to the end of the Catholic Encyclopedia's entry about the Holy Spirit. I would like to begin here by returning there:
The sins against the Holy Ghost are said to be unpardonable, but the meaning of this assertion will vary very much according to which of the three explanations given above is accepted. As to final impenitence it is absolute; and this is easily understood, for even God cannot pardon where there is no repentance, and the moment of death is the fatal instant after which no mortal sin is remitted. It was because St. Augustine considered Christ's words to imply absolute unpardonableness that he held the sin against the Holy Ghost to be solely final impenitence. In the other two explanations, according to St. Thomas, the sin against the Holy Ghost is remiss-able — not absolutely and always, but inasmuch as (considered in itself) it has not the claims and extenuating circumstance, inclining towards a pardon, that might be alleged in the case of sins of weakness and ignorance. He who, from pure and deliberate malice, refuses to recognize the manifest work of God, or rejects the necessary means of salvation, acts exactly like a sick man who not only refuses all medicine and all food, but who does all in his power to increase his illness, and whose malady becomes incurable, due to his own action. It is true, that in either case, God could, by a miracle, overcome the evil; He could, by His omnipotent intervention, either nullify the natural causes of bodily death, or radically change the will of the stubborn sinner; but such intervention is not in accordance with His ordinary providence; and if he allows the secondary causes to act, if He offers the free human will of ordinary but sufficient grace, who shall seek cause of complaint? In a word, the irremissableness of the sins against the Holy Ghost is exclusively on the part of the sinner, on account of the sinner's act.
Read the rest on the Nicene Guys site.