Hmmm... I suppose the next logical move is to delete that variable from the table, then try again. But I suspect there is something else going on here that I'm just not thinking of. Do you have backups of the database that you can revert to? That might be worth a shot as well. It strikes me as odd that the table was missing in the first place...
Also, I'm wondering if trying to access the tokens feature in LS might tell us more about what's going on. Are you using tokens (i.e., have you initialized tokens for any of your surveys)? Perhaps you could create a dummy survey (just copy some of your existing questions/groups), then initialize tokens for it and see what happens (of course, make backups before doing anyting!

).
Sorry I can't be more specific - I just need a little more information about what's going on.