UPDATED WALKTHROUGH
1. Make sure to do a clean removal and re-install first to see if this will fix the issue. If not proceed to step 2.
2. Install GPU-Z and make a note of the order of the GPUs in the drop down list at the bottom, 0 for the first GPU, 1 for the second and so on; this can be 'List A'
GPU-Z, for "List A". GTX 570 will be 0, and the 260 will be 1
3. Use command prompt (Start button, 'cmd' in the search bar and press enter) to run C:\Program Files (x86)\FAHClient\fachclient.exe --lspci and note the order the GPUs come up on this list; 'List B'
C:\Program Files (x86)\FAHClient\fachclient.exe --lspci
0x10de:0x05e2:NVIDIA Corporation:GT200 [GeForce GTX 260]
0x10de:0x0e09:NVIDIA Corporation:High Definition Audio Controller
0x10de:0x1081:NVIDIA Corporation:GF110 [GeForce GTX 570]
This is what you're looking for, and this will be "List B". In this case, the 260 will be 0 and the 570 will be 1
4. Open F@H Client and clear all the automatically assigned slots for the GPUs
5. Create new GPU slots and set the each GPU index according to "list B', and the core indices according to 'list A'. Do this for all GPUs present
Ex. gpu-index = 0, CUDA-index = 1, OpenCL-index = 1 will fold on GTX 260
6. For any GPU you DO NOT want to fold, under 'Extra Slot Options' add Name: paused Value: true
7. Save your configuration then quit and restart your client to verify that config has been saved properly.
After you set up the GPU configs correctly, the config file should look something like this
edit: NOTE: Your slot id may be different as it is based on whatever number your client assigns to it.
8. FOLD!!