The NYSE hedged its bets earlier by invoking the rarely used Rule 48, which "provides the exchange with the ability to suspend the requirement to disseminate price indications and obtain floor-official approval prior to the opening when extremely high market-wide volatility could cause delay opening securities on the exchange." The full disclosure was made on the NYSE blog:

Rule 48 is intended to be invoked only in those situations where the potential for extreme market volatility would likely impair floor-wide operations at the exchange by impeding the fair and orderly opening of securities. Accordingly, the rule sets forth a number of factors to be considered before declaring such a condition, including:

Volatility during the previous day’s trading session;

Trading in foreign markets before the open;

Substantial activity in the futures market before the open;

The volume of pre-opening indications of interest;

Evidence of pre-opening significant order imbalances across the market;

Government announcements;

News and corporate events; and,

Any such other market conditions that could impact floor-wide trading conditions.

And some other "do not panic, we have nothing under control" information dissemination by the NYSE:

The invocation of Rule 48 is in effect only for today. Previously, the NYSE invoked the rule on 11 March, 2008; 23 Jan., 2008; 22 Jan., 2008; and 12 Dec., 2007. The rule was approved by the Securities and Exchange Commission on 6 Dec., 2007. Now add 17 March, 2008 to the list. I kind of had an uneasy feeling all weekend about Bear Stearns, and felt even worse upon seeing the announcement on Sunday night. To my train buddy at Bear Stearns and his colleagues, I'm sorry to see this happen. And just for reference, here's a link to our circuit breakers. Here's hoping we don't need them today. Or any other day, for that matter. Good luck today, everyone.

Good luck indeed.