I had the same problem - my mast had a crack about half way around it - going from one hole to another to another etc. at the base where the turning blocks were mounted. Fortunately I noticed it when I removed those blocks to get ready to paint the mast. As I was sanding that area I found the crack. I repaired the mast by riveting a sleave inside the mast. The sleave was fabricated from a three foot long section of mast that I purchased from Rig-Rite. (Rig-Rite advised me on how to make this repair.) I haven't had any problems with the repaired area so far (it's been two years now)
