HELP: Lost 10 months worth of bookmarks !?

I exclusively use delicious through the firefox extension.  A few days
ago after restarting firefox, the extension asked me to sign in again.
 I guess the cookie might have expired or the extension was upgraded
or whatever reason.  But I can't remember the last time it asked me to
do that.  Anyway, after I did, my most recent bookmark was from 10
months ago.  I had been regularly using the extension over the last 10
months and probably had added hundreds of bookmarks since then. I then
signed into the website to find the same situation.

Any ideas what could have happened for me to lose all these bookmarks?
 I have no backup.