I made the same mistake. I found a USB cable and since it fitted the Kindle - I decided to use it not realising what huge mistake that was. I ended up wiping out nearly all my ebooks and I couldn't load any new books.
Rang Amazon and they helped restore the program and I was able reload my documents and books but it feels sluggish and slow when I try and open them.
I'm wandering whether I should reload the Kindle software 3.3 - will that fit the problem?