Phase I trial to study the effectiveness of interleukin-12 plus interleukin-2 in treating patients who have advanced solid tumors. Interleukin-12 may kill tumor cells by stopping blood flow to the tumor and by stimulating a person's white blood cells to kill cancer cells. Interleukin-2 may stimulate a person's white blood cells to kill cancer cells. Combining the two drugs may kill more cancer cells