Ok, maybe someone else has other factors in mind that could help on that matter.
Concerning to my experience, i had the code for the physics ball described in the manual 6.31 that worked very well in that version.
After update to 6.40 the code continued working but the ball no more had the precedent behavior, instead it rolls and slides much much more, then i had to change those properties, so the ball code never stoped working.
I must say its really strange that fact you are mentioning, i mean the code stop work, unless you changed in some way the code, like the registering procedure of the objects, or some kind of event (like even_friction) that eventually could stuck the objects somewhere..
Well, without further information its difficult, i hope someone can have other ideas. Sorry for not helping you much more.