black track texture with marbles at session beginning

when i start practice session (offline with AI) track is covered in marbles and black texture.
Screenshots here
In the beginning it is very slippery, but when session progresses it becomes more grippy and black texture gradually dissapears.

 

This issue has been already posted like 10 times. See here:
http://isiforums.net/f/showthread.php/8186-Tracks-look-blotchy

or even here (pretty long thread with mixed topics):
http://isiforums.net/f/showthread.php/8184-Build-118-Released

 

thank you, I thought it graphics bug, so I just checked this thread for same bug as mine.