1) Take out anything that was cooking in the sauce and set aside. (A Chinese spider works well for this.)
2) Get a fresh can of coconut milk, and add it to the sauce. Stir on low heat, paying attention this time, until well-blended.
3) Adjust seasonings -- the coconut milk will have added a bit of sweetness and mildness to whatever you had going, so you may need to add more of whatever else was in the sauce. Be esp. careful adding acids, like lime juice. 4) Cook down, simmering, until sauce reaches desired thickness.
5) Pour through sieve (to catch any curdled bits) over stuff you took out in step 1.
6) If you can wait to serve, wait. There will likely be some extra oil floating at the top, from the previous curdling. You can remove that with a paper towel, or a slotted spoon holding ice. (The oil will cling to the ice.)
Yes, it's a lot of steps, but better than throwing it all out and starting over!