new cards can't have due # > 32 bits

anki/collection.py

@@ -670,6 +670,10 @@ select id from notes where id not in (select distinct nid from cards)""")
         # field cache
         for m in self.models.all():
             self.updateFieldCache(self.models.nids(m))
+        # new cards can't have a due position > 32 bits
+        self.db.execute("""
+update cards set due = 1000000, mod = ?, usn = ? where due > 1000000
+and queue = 0""", intTime(), self.usn())
         # new card position
         self.conf['nextPos'] = self.db.scalar(
             "select max(due)+1 from cards where type = 0") or 0