I've run into the same issue that Pablo describes here.
if the position of an element changes from static/relative/absolute to fixed while the scroll animation is ongoing the element becomes invisible until after the scroll has come to a stop.
The 3D transform trick described in that thread worked for me with Safari and Firefox but I still see the behavior described above in Chrome and Opera Mini.
Any thoughts on a fix, workaround, hack, etc. for those two?
Thanks!