You do NOT own stock in General Motors Company. You own stock in Motors Liquidation Corporation and as soon as they sell their assets (the ones the new General Motors Company did not want) your stock will be canceled as worthless. Sell NOW. The new GM is a completely legal (key word) different company than the old GM (which was a Corporation, notice the new GM is now a Company), which is now Motors Liquidation.
The new (current) General Motors Company does not have any public stock issued. They plan to issue stock sometime during the spring of 2010.
Please do not invest in companies going into bankruptcy without learning all about bankruptcy proceedings.