Thanks stevesr0, i am not sure that the problem is 100% the same( i have had a working persistent image for let's say 2-3 weeks),but the lesson i learned(my working around solution with new persistent image) is to always have minimum 1/3 of knoppix.img free/not in use and the same for ramdisk (1/3 of ramdisk minimum,always free),and never try again to use the option "Overwrite/update stored system configuration". I have 1GB ram,350 MB SWAP and i use a 3.5 GB knoppix.img size.