@barsoforion - I was able to download that story as mobi and load it via USB to my Kindle 3g without any problems. Download to epub and convert to mobi also worked.
As it says in the FAQ
, mobi support in FFDL is not the greatest. I generally recommend that everybody download to epub and then convert to mobi--if that works, I suggest using it. If you use the Reading List plugin to load your device, the conversion will be done automatically.
I have a how-to
about using Reading List with FFDL and devices.