In the immediate term, pressure should be put on the Rwandan leadership itself to rein in Nkunda; in the short term, Monuc should be supplemented by a large EU force; in the longer term, as eastern Congo seems ungovernable from Kinshasa, I see no option but the creation of a buffer state on the western shores of Lakes Kivu and Tanganyika. This could be achieved by regional forces with Monuc-EU backup.
Worth looking into, though I'm not at all convinced that the ethnic cleavages or the resource expropriation issues at the heart of the conflict would be solved by a buffer state. Still, Ambassador at Large is always intrigued by the possibility of partition, if done properly, when a country clearly cannot work as constituted. If ever there was a country that can't work as constituted, it's Democratic Republic of Congo.