bojan, I have heard of this before, and to be honest I can't quite remember what it means, but it dose have something to do wuith the lens you have attached, I think, sorry i can't be of much more help, but i do know this is quite a common occurance.
Leon
Ps Have a look here or here
http://www.richardsnotes.org/archive...ontact-points/
http://simple-pc-help.com/support/er...FQUupAodixq_ag