here is the list Ameritrade~pick one: (this is only SOME of them)
"Some of the reasons a stock may be restricted to closing transactions only include:
1 ~ Corporate Actions in which a lack of information, confusing terms, or unclear objectives may be involved. All corporate actions should be transparent as to objectives. 2 ~ Apparent or possible fraudulent activity by a company or it's officers, with potentially manipulative actions to affect a stock price. 3 ~ Frequent unsubstantiated press releases in an attempt to affect the stock's price. 4 ~ Deceptive or contradictory statements regarding past or projected performance. 5 ~ Corporate Identity Theft 6 ~ Valid companies associated with third parties (i.e. transfer agents, consultants, etc) that have shown a predisposition to any of the above activities. 7 ~ Companies known or suspected to be involved in Money Laundering activity"