Having the same thing happen to an entry for today that started the problems last week (this software is choking on the word x*anax when it's spelled properly and I can't submit the post), doing a search for that word in the directory I'd downloaded last week, my system's search function found that very same word in an old sql file. One that I'd saved and downloaded on March 1st of this year.
And comparing it to the file I downloaded last week, it's 9Mb bigger! All of the entries from before March 1st have been saved! I'll only have to do the rest of this year, which shouldn't really take all that long.
And to help me get those files back in, Ellislab is letting me take advantage of the three month free help trial, even though I bought and paid for this software back in 2009. (I first installed it back in March, which is when I saved that old sql file.)
Yay!
It is a good Christmas after all!