oops......probably, its the wife's machine, I forgot about that.
On the 2x680's I'm still getting the same 'cudaminer has stopped working' if I try any config except auto or k8x24.
Auto tells me 20x12 should be best, but manually entering that just crashes.
cudaminer-2013-12-10\x86>cudaminer.exe -D -H 1 -i 0 -d 0,1 -l k20x12
-m 1 -C 1 -o stratum+tcp://ltc.give-me-coins.com:3333 -O
[2013-12-18 13:06:18] Starting Stratum on stratum+tcp://ltc.give-me-coins.com:3333
[2013-12-18 13:06:18] 2 miner threads started, using 'scrypt' algorithm.
[2013-12-18 13:06:18] Stratum session id: 50298b34787f00001
[2013-12-18 13:06:18] Stratum difficulty set to 16
[2013-12-18 13:06:19] DEBUG: job_id='1387371954 4569' extranonce2=00000000 ntime=52b19db2
[2013-12-18 13:06:19] GPU #1: GeForce GTX 680 with compute capability 3.0
[2013-12-18 13:06:19] GPU #0: GeForce GTX 680 with compute capability 3.0
[2013-12-18 13:06:21] DEBUG: job_id='1387371988 4570' extranonce2=00000000 ntime=52b19dd4
[2013-12-18 13:06:21] Stratum detected new block
Program crash
Not a great problem, just thought you might like to know

EDIT: How's this for wierd? - although manually entering the 8x24 config worked twice, after trying 'auto', even that now causes the program to 'stop working'. Tried a reboot, and that didn't help - now only 'auto' works?