I have almost learned to live with this but I figured I would check back again to see if anyone has a work around.
I have two 642s with the same problem. They have different firmware, one old, 531 I think, and one current. Both will switch out of progressive scan from time to time when I start up, never during a viewing. If I go to the menu and change to regular and then back to progressive all is fine. It primarily seems to happen to -/+R and +RW discs and I have seen other posters here with the same problem so it seems to be a bug. Of course Philips is oblivious and wanted to charge me $15 to "research" this problem.
I can live with this long drawn out turn on sequence if I have to but I figured if smarter people had figured it out I would be dumb to keep doing what I am.
Thanks in advance.