Probably to avoid chances of insiders, including spin-off and debt investors, from front-running. More cynically, to allow their friends to dump stock at the end of the day; but I don't think they run that kind of shop over at ORI. They should have done it over the weekend to allow everyone a fair shake; in that regard, I think they blew it.
It definitely will not affect the regular dividend. It was already voted on by the BOD. It's a done deal. But I have no knowledge on the details of the spinoff or for whom it's a taxable event.
Once ORI sheds this division, what remains had an operating profit of .88 last year. And I expect it to be higher in 2012. I think the stock should head back to 12. In recent years the dividend increase has been .01 per share. Without that lead weight, the dividend increases could start being greater in 2013. It would be nice to have more details.