A while back we found the most outlandish corner case I've ever seen.
In Sybase you'll run into it, sometimes, if you:
select into a table and the select is from a view and the view contains a union and the destination table isn't in the same database as the tables in the view.
To boot, this only occurred in the live environment, we could not reproduce it in either of development or three separate test environments with various amounts of data.
Remove any one of the conditions and everything works fine.
I rewrote the query.