I don't know if it's moot at this point, but a corrupted ISO doesn't seem to be the cause of the problem.
There is still the issue of method of creation; the condition of the SD card; and how your SD Card Reader is connected to your system...and at what point 'it gives up'.  What do you see?
Now that you have a working copy of Navigatrix open a terminal.  You can check the state of your SD with
Code:
sudo badblocks -n -s -b 2048 /dev/sdX
X being the location of your card (a,b,c,d...).  Run 
df -h   Match the size with name. 
Quote:
...
/dev/sda1                     228M  148M   69M  69% /boot
/dev/sdd1                     917G  402G  469G  47% /media/wadda/Toshiba
/dev/sdc1                     917G  681G  190G  79% /media/wadda/Terry
/dev/sdb1                     3.8G  2.7G  1.1G  72% /media/wadda/9ED5-DA9C
 In this case it would be 
/dev/sdb.  It must be unmounted.
An easy method to 
unmount it is to click the rectangle/triangle icon next to the device in the 
File Manager.  You could also run 
sudo umount /dev/sdX1 from the terminal
Badblocks is a slow process that non-destructively checks for bad sectors.  Depending on the horsepower of your machine you could increase the default chunk scan by adding 
-c 128Quote:
       -c number of blocks
              is the number of blocks which are tested at a time.  The default
              is 64.
If it's straining already, reduce 
-b 1024 or remove it entirely.
More info can be found with 
Code:
man badblocks
Another method, which will fix 'everything' wrong, but without a progress bar  is
Code:
sudo fsck.vfat -atvw /dev/sdX1
Again 
X is the location of the card.
Quote:
fsck.vfat -atvw /dev/sdxx
Run a FAT32 file system check and badblocks scan with progress info
  -a       automatically repair the file system
  
  -t       test for bad clusters
  
  -v       verbose mode
  -w       write changes to disk immediately
/dev/sdxx ? the partition to check, (e.g. /dev/sda1 for first partition on first hard disk)
NOTE: Never run fsck on a mounted partition!
More info can be found with 
Code:
man fsck.vfat