Well I removed the white stuff, (what I could actually), I also tried to smell it but it does not smell, so really don't what it is, I'm gonna take your words then and guess it was grease (or 20 years old mayonnaise
), then I checked the loading belt and it looks like it's still pretty solid, so don't think it was that.
I also removed the dust where there was, I found a little on the laser lens and removed it very gently without using any products.
After that I turned on the player again and tested the drawer, it actually opens and close a little faster and also more silently than before, so my guess is I "fixed" it.
Then I closed back the player and watched a couple movies as a way to "test" it, so I finally watched the Small Soldiers and Tomorrow Never Dies copy I got more than 3 months ago (actually, it was the day just after I "broke" my D925, what a luck...), anyway I digress, the point is it's working great (for) now, and the picture is a little better than yesterday (and is quite good actually), so dusting it off was not a bad idea.
Anyway, thanks for your views on the mysterious substance, but I managed to fix it myself (for once
)