Looks like we've had a major glitch, folks. No idea what could have caused it, but everyone's subscribed threads have been deleted from the database.
Very odd. I'm glad it was the subscribed threads table that got zapped, though and not, say, the threads table, or the members table...
I don't think there's anything I can do about it; the data is gone. You'll have to re-add them manually.
There is possible a sunny side to it, though -- with these all deleted, switching on email notification again might actually be feasible. It'll probably take months before the subscribed thread database rebuilds itself to the point where it's sending out as many emails as it was before, especially as many of those emails probably went to dead email accounts or to members who no longer post (and who therefore won't be likely to resubscribe).