Stock futures freeze as tumble worsens Fri Oct 24, 2008 7:17am EDT LONDON (Reuters) - Stock index futures tumbled so sharply in European trade on Friday, they had to be frozen at several points in the morning. By 6:27 a.m. EDT December Dow Jones futures were down 6.2 percent, Standard & Poor's 500 futures were off 6.6 percent and Nasdaq 100 futures were down 6.6 percent. All three contracts lost the maximum amount permissible before the start of futures trading in the United States. "We are in a panic mode, I don't know how else to describe it and when...