Now I understand why you and your fellow travelers deny Paul wrote Hebrews because if he did your little doctrinal house of cards comes tumbling down.
Why would I say that Paul wrote Hebrews when the evidence points to the contrary? I am fully persuaded that Paul didn't write Hebrews for the aforementioned reasons that brother steko mentioned and others too. Much of what was said in Hebrews does not line up with that which Paul preached in Romans through Philemon. One example I already showed in response to TL's comment and here's another example. The writer of Hebrews (written to Hebrews) writes:
Hebrews 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
Hebrews 6:5 And have tasted the good word of God, and the powers of the world to come,
Hebrews 6:6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
While Paul writes that those of us who have trusted the Lord after hearing and believing the word of truth, the gospel of our salvation are sealed with that Holy Spirit of promise until the redemption of the purchased possession!
Ephesians 1:13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise,
Ephesians 1:14 Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
It's not hard to see that we have eternal security while the Hebrews don't!