Fixed.
There was a problem with group=<amanda group> and groups=yes in my amanda 
files for xinetd. (thanx to Gene Heskett ;-)) As I understand now --  "group" 
parameter is necessary because of root is owner of runtar and group have r-x 
on it.
Now all of previous errors are fixed.
BTW. Thanx for all advises -- it was a grait surprise for me that so much 
people ready to help newbies. I like amanda more and more ;-)