Reportedly (http://news.bbc.co.uk/1/hi/world/africa/7306325.stm), Democratic Republic of the Congo is cancelling or renegotiating many of its mining contracts, because "none of the contracts met international standards".
It could be a smart move. African mining deals can give foreign companies returns on their investment which are laughably high. The company only has to operate for a month and it has recovered in profits all of its original investment. OK, Africa's sometimes risky, but not that risky.
It could be a smart move... if the renegotiated deals are transparent. Otherwise, the new terms could be similar to the old ones, but with a different minister or civil servant pocketing a bribe, and investors thinking that the government is volatile and corrupt. The current Congolese administration has overseen a good macroeconomic performance given the extraordinarily difficult circumstances, and hopefully it will continue to improve the economy.