When a company is involved in bankruptcy proceedings, the letter "Q" is added to the end of the company's stock ticker symbol. When a company emerges from bankruptcy, in most cases the plan of reorganization will cancel the existing equity stock. The SEC advises the public to read a company's proposed plan of reorganization before purchasing stock in a bankrupt company.
For more information about the impact of bankruptcy proceedings on securities, please read the SEC's online publication, Corporate Bankruptcy. http://www.sec.gov/investor/pubs/bankrupt.htm